This question came in my exams, I was able to find the value of a+b but not x, please explain how to do this question, our syllabus was of lines and angles and triangles from class 9th 

cointerior property
a+2b+2a+b=180
3(a+b)=180
a+b=60
also angle sum property of triangle
2b+2a+∠ACB=180
2(a+b)+∠ACB=180
120+∠ACB=180
∠ACB=60
then angle sum property of quadrilateral
x+90+90+60=360
x+240=360
x=120
hence (a+b)/x
          =60/120
          =1/2