SAT Mathematics Practice Test 7

The figure is a quadrilateral, so the sum of the measures of its interior angles is 360°. The value of x can be found by using the equation 45 + 3x = 360. Subtracting 45 from both sides of the equation results in 3x = 315, and dividing both sides of the resulting equation by 3 yields x = 105. Therefore, the value of x in the figure is 105.