The basic identities related to speed, velocity, accleration numerical problems are:
V = u+at
a = V-U/t
S = ut+1/at2
2as = v2-u2
The first identity is followed when the intial velocity, acceleration and time is given and you have to find out the final velocity of a moving obejct.
The second identity is followed when the initial, final velocity and time is given and you have to find the acceleration.
The third identity is used to find the distance when you know the initial velocity,the acceleration and the time.
The last one is used when you have to find out the travelled distance but you don't know the time. The initial and the final velocity is given and the acceleration is present.