Official Explanation
You are given the measure of one acute angle (a) and one obtuse angle (g). Because any acute angle in this diagram is supplementary to any obtuse angle, then \(11y + 4x − y = 180,\) or \(4x + 10y = 180.\) Because angle d is equal to angle a, then \(5y + 2x − 20 = 4x − y,\) or \(2x − 6y = −20.\) You can set up a system of two equations with two variables:
\(2x-6y=-20\) ------>____\(-4x+12y=40\)
__________________________\(4x+10y=180\)
_____________________________________________
__________________________\(22y=220\)
__________________________\(y=10, x=20\)
h is one of the acute angles, therefore, h has the same measure as a: \(4x − y = 4(20) − 10 = 70.\)
Answer: A