Question

t=2,s=400,a=?..........

Answer 1

$400 \div 2 = 200$

Answer 2

HEY MATE HERE IS YOUR ANSWER

Equations of motion use here which is

$\huge\boxed { v = u + at}$

$\huge \boxed {s = ut + 1/2 at^2}$

$\huge\boxed {V^2 - U^2 =2as}$

According to question you can use these equations for solving.
HOPE IT WILL HELP YOU