Two lines intersect, forming four angles. One of the angles measures 5x − 10 degrees and its adjacent angle measures 3x + 30 degrees. What is the measure of the angle vertically opposite to the 5x − 10 degree angle?
Show answer & explanation
Correct answer: D
Explanation
Adjacent angles are complementary
(5x − 10) + (3x + 30) = 180
8x + 20 = 180
8x = 160 ⇒ x = 20
Now angle = 5x − 10 = 100 − 10 = 90°
Vertical opposite angles = are equal ⇒ 90°