Question

How do you solve this?

Answer 1

The h in the question would be 100ft which was the wall height. The v should be 100ft/sec. The ball is launched from the base so the hi would be 0. 
The calculation would look like this:

h= -16t^2 + v*t + h
100= -16t^2 + 100*t + 0
-16t^2 + 100t - 100=0          -----> divide by -4
4t^2 -25t + 25  =0                   -----> split -25t into -20t and -5t
(4t^2 -20t)  (-5t + 25) =0         -----> simplfy 
4t (t -5)     -5 (t -5) =0
    (4t-5)           (t-5)
t= 5/4=1.25  ;    t= 5

The ball will be higher than the wall at 1.25< t  <5