if you knew calculus this problem would take like 2 seconds, but since we are working with maybe Algebra 2, you have to use the equation as it is and find where h(x) is 0, because that is the height of something when it hits the ground. Meaning, you have to factor this and solve it for x. Here's your equation:
h(x) = -16x^2 + 60x +16. Use the quadratic formula to find that the values for x are -.25 and 4 seconds. Of course time cannot ever carry a negative value, so the answer is 4 seconds. It takes the ball 4 seconds to hit the ground.