Answer:
t = 3 seconds
Explanation:
You can think of this as a quadratic and find the zeros. i will use x and y to make it easier.
y = -16x^2 + 48x
y = (x)(-16x+48)
y = (-16)(x)(x-3)
This means your zeros are at x = 0 and x-3 = 0, so 0 and 3.
0 is when the ball leaves the ground, so 3 is when it returns.