A mango fruit falls down from a tree due to its weight, with an initial velocity of 15m/s. Find the displacement and velocity after 4 seconds.

I don't see why the initial velocity would not be zero, unless it was knocked downward from the branch.

Downward velocity increases by an amount g*t after t seconds.
g is the accleration of gravity, 9.8 m/s^2

After 4 seonds, velocity is higher by 39.2 m/s. Add that to the initial velocity.