<span>3.19459 seconds
Since we've been given the equation for how high the ball is at t seconds, all we need to do is solve for a height of 0. So
h = 67 - 5t - 5t^2
0 = 67 - 5t - 5t^2
And you should immediately notice that we have a quadratic equation with A = -5, B = -5, and C=67. Use the quadratic formula to determine the roots of -4.19459 and 3.19459. Since we can't have negative seconds, that means that the ball will hit the ground 3.19459 seconds after it was thrown.</span>
