I don't understand how to do this problem

find s(t) for a(t)= 3t^2, v(o)= 20 s(o)=5

This looks like a motion problem in which s(o) is initial location and v(o) is the initial velocity (ds/dt) at t = 0, and a(t) is the (variable) acceleration. Solve by integration.

v(t) = v(o) + t^3
s(t) = s(o) + v(o)*t + t^4/4
= 5 + 20 t + t^4/4