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