What is the final velocity of a car that accelerates 4m/s2 for 5 seconds if it’s starting speed was 5m/s? (Which equation should I use?)

Answer:
Work out which of the displacement (S), initial velocity (U), acceleration (A) and time (T) you have to solve for final velocity (V).
If you have U, A and T, use V = U + AT.
If you have S, U and T, use V = 2(S/T) - U.
If you have S, A and T, use V = (S/T) + (AT/2).