Explanation:
Use SOH-CAH-TOA.
Sine = Opposite / Hypotenuse
Cosine = Adjacent / Hypotenuse
Tangent = Opposite / Adjacent
You're given an angle, the adjacent side to that angle, and the hypotenuse. So use cosine.
Cosine = Adjacent / Hypotenuse
cos 37° = 48 / x
Multiply both sides by x.
x cos 37° = 48
Divide both sides by cos 37°.
x = 48 / cos 37°
If desired, use a calculator to evaluate.
x ≈ 60.1