8x+1+12=848x+13=848x=84-138x=71x=71/8x=8.815
8X+X+12=84解:8X+X=84–12 8X+X=72 (8+1)X=72 9X=72 X=8
(8+1)x+12=84 9x+12-12=72 9x÷9=72÷9 x=8
9X+12=84 X=84-12 9X=72 X=72÷9 X=8