6x(2x - 1) - 3(3x - 3y + 1) =12x^2 - 6x - 9x + 9y - 3 =12x^2 - 15x + 9y - 3
2(5x - 4y + 1) - 3(3x - 3y + 1) =10x - 8y + 2 - 9x + 9y - 3 =10x - 9x - 8y + 9y - 1 =x + y - 1
6x(2x - 1) - 3(3x - 3y + 1) =
12x^2 - 6x - 9x + 9y - 3 =
12x^2 - 15x + 9y - 3
2(5x - 4y + 1) - 3(3x - 3y + 1) =
10x - 8y + 2 - 9x + 9y - 3 =
10x - 9x - 8y + 9y - 1 =
x + y - 1