Answer
$x \approx 9.5$
Work Step by Step
We are given the measure of the hypotenuse of the right triangle and the measure of one of its angles; we can use the cosine ratio to find $x$, which is the measure of the side adjacent to the angle.
The cosine ratio is given as follows:
cos $x^{\circ} = \frac{adjacent}{hypotenuse}$
Let's plug in what we know:
cos $58^{\circ} = \frac{x}{18}$
Multiply each side by $18$:
cos $58^{\circ}(18) = x$
Multiply to solve for $x$:
$x \approx 9.5$
