SAT Mathematics Practice Test 3

Since $180-\mathit{z}=2\mathit{y}$ and $\mathit{y}=75$,
it follows that $180-\mathit{z}=150,$ and so $\mathit{z}=30$.
Thus, each of the base angles of the isosceles triangle on the right has measure $\frac{180°-30°}{2}$.
Therefore, the measure of the angle marked $\mathit{x}°$ is $180°-75°=105°$ °,and so the value of x is 105.