First you should now that 4x° and the 5x° are supplementary angle so they both equal to 180° therefore 4x°+5x°=9x°=180° or 180°=9x then divide by 9 on both sides of the equation and you will get x=20
Now you found x=20 since the only angle you need to solve for is the 4x° since that is the one that is inside the triangle and is needed to solve y°. PLUG IN X in 4x. 4x°= 4(20) then 4x°=80! :D
So now the triangles have the following interior angles 80° and 48°and y. Since the in a triangle the angles MUST add to 180° So put it in together 48+80+y=180 then isolate y or just subtract 48 and 80(y=180-80-48) FROM BOTH SIDES of the equation then the answer would be y=52°
