Answer
$x = 61^{\circ}$
Work Step by Step
Since we have the measure of the side adjacent to an unknown angle and the hypotenuse of the right triangle, we can use the cosine ratio to find $x$, which is the measure of the unknown angle.
The tangent ratio is given as follows:
cos $x = \frac{adjacent}{hypotenuse}$
Let's plug in what we know:
cos $x = \frac{31}{64}$
Take the $cos^{-1}$ of the fraction to solve for $x$:
$x = 61^{\circ}$
