化简80-x=3600x÷1200
80-x=3x
80=4x
x=20
如上所述过程
1200（80-x）＝4x900x9600-1200x＝3600x9600＝3600x+1200x9600＝4800xx＝2
96000-1200x=3600x9600=4800xx=2
1200（80-x）＝400×900x80-x＝3x4x＝80x＝20
