eq^2: 7x=84 divide 84 by 7 which is 12.
therefore x is equal to 12. Then
1) take that 12 you got in equation 2 and substitute in equation 1 which is:
7x-12y=180
7(12)-12y=180
84 -12y=180
-12y=180-84
-12y=96 ............divide both sides with -12
-y=8 (×-1) both sides
y= -8
therefore 7(12)-12(-8)=180