Answer
$x = 12$
Work Step by Step
According to theorem 6-19, the base angles of an isosceles trapezoid are congruent.
Let's set the two base angles, $\angle S$ and $\angle R$, equal to one another to find the value of $x$:
$5x = 60$
Divide both sides by $5$ to solve:
$x = 12$
