Well, it's a quadratic, so it has to have 2 roots. 'Roots' meaning when its velocity is 0 or in this case, the ball hits the ground. So, let's just throw this into the quadratic equation. Remember, the quadratic equation is:
and

To plug values in, let's first rearrange the equation, so it's easier to plug in:

Plug in (a = -5, b = -10, c = 65) and since we are solving for t, not x:

and

Solve:
and

Simplify:
and

Since time cannot be negative, your answer is
the ball takes 2.742 seconds to hit the ground.