Ok, so first this is a system. You have: 8x+12y=3200 And X+y=300. That means y= -X + 300. If you replace "y" in the first equation with -X+300, it would be 8x+12(-X+300)=3200. If you simplify that, X will be equal to 100. Now go back to the second equation, which is X+y= 300. Now that you know X is 100, you can subtract it from 300 to find y. So, X=100 and y=200! Hope this helps!!!