To solve you need to set the equation equal to 6 (the height at which the player caught the ball.
6 = -16t^2 + 70t + 4
Next put the equation in standard form by subtracting 6 from both sides
-16t^2 + 70t - 2 = 0
This equation can be simplified by dividing by 2
-8t^2 + 35t - 1 = 0
This equation cannot be factored, but we can use the quadratic formula to find a value for x. Using the equation above we can find the values for a=-8, b = 35 and c = -1.