urgent! pls help!

Question

A ball is thrown from an initial height of 6 feet with an initial upward velocity of 21 ft/s. The ball's height h (in feet) after t seconds is given by the following.

find all values of t for which the balls height is 12 feet

Answer 1

The height equation is missing. However, assuming this is for earth where gravity,g=-32:

h(t) = gt²/2+vt+h₀

When h = 12

-16t²+21t+6 = 12

-16t²+21t-6 = 0

t = (-21±√(441-4(-16)(-6)))/-32 = (-21±7.55)/-32

t=0.42, 0.892 seconds