Because of the level. Vertical and oblique are all equal, so there are

3+4+X=3-2+2Y-X

7+X= 1+2Y-X

6=2Y-2X

y-x=3( 1)

3-2+2y-x=2y-x+Y+X

So y+x= 1(2)

( 1)-(2)

Y=2

So we can get the results,