Equation 1:
x = (5y+11)/2
Substitute equation 1 to 2:
-2((5y+11)/2)+ 3y=-9
-2/2 = -1 thus -1(5y+11)
Continue...
-(5y+11)+3y=-9
-5y-11+3y =-9
(-5+3)y= 11-9
-2y = 2
y=-1
Substitute y into equation 1:
x=(5*-1+11)/2
x = 6/2=3
So y=-1 and x =3
2/3x + 7 = x-7
+7 +7
---------------------
2/3x + 14 = x
-2/3x -2/3x
----------------------
14 = 1/3x
*3 *3
-------------
42 = x
Hope this helps! :)