I dont understand how to solve this

Question

A golfer takes a swing from a hill twenty feet above the cup with an initial upwards velocity of 32 feet per second. How long does it take the ball to land on the ground near the cup?

Answer 1

h = 20 + 32t - 16t^2

0 = 20 + 32t - 16t^2

0 = 5 + 8t - 4t^2

0 = 4t^2 - 8t - 5

0 = ( 2t - 5)( 2t + 1 )

t = -1/2 is disqualified

t = 5/2

2.5 seconds