The final answer is (65, 60).
 x + y = 125 
 - y - y
-------------------
 x = 125 - y
12(125 - y) + 6y = 1140 
1,500 - 12y + 6y = 1,140 
 1,500 - 6y = 1,140
- 1,500 - 1,500
------------------------------
 -6y = -360
 ------- --------
 -6 -6 
y = 60
 x + 60 = 125
 - 60 - 60
-------------------
 x = 65