Answer:
you know that you have the Opposite side and the Adjacent side. therefore you would use Tangent (T= O/A)
because you are finding the angle you would go Tan^-1(12÷20) =31°
it is 12÷20 because O/A and the 12 is the opposite side therefore It would be O and 20 is the adjacent side therefore equaling 20 so O/A = 12/20
Your answer is 31°