The triangle height is calculated by Pythagorean Theorem height^2 = 15^2 - 9^^2 height^2 = 225 - 81 height^2 = 144 height = 12
We can calculate the value of Angle a cosine (a) = adj / hyp = 9/15 = .6 arc cosine (a) = 53.13 degrees angle b = 180 -90 -53.13 angle b = 36.87 degrees tangent b = height / x tangent 36.87 = 12 / x x = 12 / .75 x = 16