Y=5
The square has to equal 180 and the angles in clock wise order are 68, 87, 93, and 112. So the unmarked angle of the small triangle is 87 so y^2 would have to be 25 and 2x would have to be 68 so y=5. Or you could have done 68+(3x-15)+y^2=180 and solve from there.
