H(t) = -16t² + 19t + 5
Since you are given H in feet, just plug the number into the equation and solve.
4t = -16t² + 19 t + 5
0 = -16t² + 19t + 5 - 4t
0 = -16t² + 15t + 5
5 = -16t² +15t
16t² - 15t= -5
t(16t - 15) = -5
t ≠ -5 because the ball can not be under the ground
so you are left with 16t - 15 = -5
16t = 10
t = 10/16
Simplify
5/8 in decimal form that is
0.625s