first the ball dropped at time = 0 seconds
so by substitute t= 0 in the equation you get that the hight = 150 ft
h(0)=-16.1(0)^2+150
so , h=150 ft
second when the ball just touches the ground the hight will be 0 , so by substitute by h=0
we get
0=-16.1t^2+150
t^2 = -150/-16.1
t= 3.052 second
