h e l p ; - ;
idk how to manipulate it ; - ; .

Answer:
Step-by-step explanation:
Part A
To keep it simple, I will use v instead of vi, x instead of triangle x and t instead of triangle t.
The equation becomes: x = vt + 1/2at^2
Solve for a:
x = vt + 1/2at^2
x - vt = 1/2at^2
(x - vt)*(2/t^2) = 1/2at^2*(2/t^2) = a
a = 2(x-vt)/t^2
or writing in the right format
a = 2(Δx - viΔt) / Δt^2