In this problem, you must use SohCahToa which basically means:
Sin - opposite over hypotenuse
Cosine - adjacent over hypotenuse
Tangent - Opposite over hypotenuse
So in this picture we have 4 -which is on the opposite side of x - and a 5 -which is the hypotenuse of the triangle. This means we must use sin.
Using a calculator you put in:
Your answer is 53.13 degrees