Respuesta :
The problem provides us with a formula which relates the distance as a function of time. Since the problem wants to find the time given the distance of 50 feet, then this formula is useful. Just substitute s = 50 and solve for t.
50 = -16t + 70t + 3
Solving for t,
t = 0.87 s
50 = -16t + 70t + 3
Solving for t,
t = 0.87 s