You can use either sine, cosine, or tangent to find the measure of angle x, but since the lengths of the adjacent leg and the hypotenuse are already given, cosine will be the easiest to use. The adjacent leg is 5 units long, and the hypotenuse is 12 units long.
Remember, cos(x) = adjacent / hypotenuse.
cos(x) = 5/12
( ) both sides
(cos(x)) = (5/12)
Simplify ((cos(x)) ⇒ x)
x = (5/12)
Use calculator (make sure it is in degrees, not radians)