Units are more important than the number ; the "thing that it is" is more important than the units
... even more important is whether it is an instantaneous condition , or an ongoing process
... maybe most important is whether the thing describes an object , or the environment the object is in .

You should draw a sketch of each situation , label relevant quantities on the sketch , in symbols
. . . the ones you "know" values for , and the ones still "unknown" => especially the answer subject !

All of your statements should begin with a subject symbol , before the predicate "=" , then the object.
. . . the symbol "=" can be read as "is" ; but you should recognize (and try to use) more precise meanings
      including : "is defined as" , "causes" or "produces" , "comes from" or "is caused by" , "is determined by" ...
      . . . (did you notice that none of this list is reflexive? that none are symmetric? ... which ones are transitive?)

The first statement in your answer should be a general statement , in symbols , about the situation or scenario
. . . we try to use meaningful symbols for nouns - often abbreviations for a phrase
      we routinely modify nouns with adjectives and prepositions ; these are written as subscripts .
. . . the "climax statement" should begin with the desired unknown as its subject . . . (earlier ones don't need to)
. . . perform the same computations on the units that you do on the numbers

. . . you'll learn much more (with little more effort) if you de-brief yourself after getting the answer :
      a) typical values at the scale of this scenario : is the answer the "right size"? why is it so big or so small?
      b) improve your effectiveness : what did I get stuck on? what got me un-stuck? how to be stuck for less Δt ?
      c) how physical quantities relate to each other: if given#n was 2× as big, result#a would be ____ × bigger ...

- - - choose an origin for time and location - - - to make important condition properties - - - zero - - -

If you start your stopwatch at the "right" instant (defining t=0) , you can make the initial time t_i = 0
      so that Δt   (= t_after - t_before)   becomes just   t .
. . . you might want to make x₀ = 0 , or v₀ = 0 (or at least known) , or ...

Important Statement #3 about How the Universe Works :

Force being applied to an object for a time duration CAUSES the object's momentum to change.
... the Force is applied by the subject - distinct from object - as the object's environment .
. . . While the Force is being applied , a process is occurring (Impulse) :   _{into object}F_{from subject} Δt = Δp_object   .

Re-arranging the two changes into a ratio =>   _{on object}F_{by subject} = Δp/ Δt
. . . Force depends on location ... IF   F(r) has no dis-continuity , the limit as Δt→0   will exist ... (even if F(r) is not smooth)
=>   F = dp/dt , as a derivative .

Since the object's mass is constant ,
=>   F = m· Δv / Δt =   m·a . . .
  This acceleration a has direction ... same direction is positive as for x , and v , and p .
. . . (by now you habitually indicate the "+'ve" direction on your sketch ...)
  this a is the average value that exists for the duration   Δt   of the applied Force . . .
. . . connects the earlier condition (v₁) with the later condition (v₂) .

Since momentum , as a function of time has to be smooth through time (with no "corners") , the limit as Δt→0 exists , and
=> a(t) = dv(t)/dt   , as a derivative .

(Reminder, definition of average velocity) Important Kinematic Equation #1 :   v_avg ≡ Δr / Δt
=> place story line :   r_start + v_avg·Δt  =  r_end                             (acceleration is not explicit)

(definition of average acceleration) Important Kinematic Equation #2 :   a_avg ≡ Δv / Δt
=> motion story line:   v_start + a_avg·Δt  =  v_end                           (displacement is not explicit)

IF acceleration is constant during the interval Δt :   v_avg  =  v_start + ½ Δv  =  v_end − ½ Δv  =  ½ ( v_start + v_end ) .
=> place story w/ accel : Kinematic Equation set #3 :   has 3 different "wordings" mixing the info of #1 and #2 )
. . . (a) . . . r_start + v_start·Δt + ½ a_avg (Δt)²  =  r_end       (ending velocity is not explicit)
. . . (b) . . . r_start + v_end·Δt − ½ a_avg (Δt)²  =  r_end         (starting velocity is not explicit)
. . . (_) . . . r_start + ½ (v_end² − v_start²) / a  =  r_end                               (how to divide by a vector? Re-Write!)
. . . (c) . . . v²_start + 2 a_avg·Δr  =  v²_end                             (time duration is not explicit)
      CAUTION : form "c" requires scalar multiplication of vectors ... the directions of   a and Δr   are important !
      caution : form "c" requires you to identify   v²   with two locations on a diagram ... it discards direction of both velocities

IF acceleration changes during the interval Δt : the acceleration change-rate is cslled jerk .

- - - NOTICE - - - which quantity - - - does NOT explicitly show - - - in each equation above - - -

Solvable Kinematic scenarios can only have 2 __TWO___ of these quantities as unknown
. . . make sure the other 3 are __ON_YOUR_DIAGRAM__   . . .(4, if you have x_i and x_f , instead of Δx )
Your diagram should tell you whether you need to "sub-contract" to obtain a value from a preliminary scenario ...

Solve part (a) for a's unknown , by using whichever equation is _missing_ part b's unknown .
Read the equation as words ... appropriate to the scenario ...
... then , do symbolic algebra to isolate a's unknown . . . RE-READ YOUR RESULT as words
... when satisfied that the relationship is reasonable, plug numbers [ WITH UNITS ! ] and compute your result
      . . . THINK ABOUT whether it's ABOUT RIGHT , size-and-unit-wise !
... finally , you can use any of the OTHER equations to calculate b's unknown
      . . . even those which need to use a's _now_known_ .

Dynamic scenarios _imply_ a by telling F and m . . . or Δv , by telling Δp and m . . . or combinations with Δt

- - - - the KEY is - - - to TRANSLATE the STORY-LINE - - - to a SYMBOLIC STATEMENT - - -

Process quantities ... displacement (Δr) , boost (Δv) , Impulse (FΔt) , Action (p·Δx) ... add sequentially
  make sure the durations being added DO NOT OVERLAP . . . change = change   so , there is always one Δ in each term !

Condition vectors ... location , velocity , acceleration , momentum , Force ... are added at the instant of that condition
. . . it is the Sum of simultaneous Forces that cause the effected mass to accelerate (at that instant) : Σ F = m a .