It's an isosceles triangle so both sides are the same. The missing side is 30
X is equal to 2. you can set them equal to each other because they are corresponding angles, which means they are congruent.
So you want height to be 0 so you plug zero into the height and solve from there. You subtract 192 from both sides to get -192=-16tsquared. Then you would divide by -16 and end up with 12 = t^2. Then you find the square root of 12 and get t = 3.464 seconds.