✔ 最佳答案
3x - y = 9; solve for y first. -y = 9 - 3x then y = -9 + 3x or y = 3x - 9.
Now that you have that, plug in 3x - 9 into the other equation where y is. it should look like this: 2x + (3x - 9) = 6
5x - 9 = 6
x = 15/5 = 3
now, use that as x and plug back into the first equation to get y:
3(3) - y = 9
y = 0