2x + 3y = 630 x + y = 245 then you want to get rid of x so in the second equation × by -2 and get -2x -2y =-490 subtract this equation from the first to get y=$140 substitute 140 in for y and get x= $105 and 2x=210 and 3y=420 210 +420=630
The reason is because it is not just 6 it is - 6 so when there are two negative numbers they don't subtract they add if it was 6n then it was to be subtracted
