解:4x+20%x=13.86 4x+0.2x=13.86 (4+0.2)x=13.86 4.2x=13.86 x=13.86 / 4.2 x=3.3
(4+20%)x=13.864.2x=13.86x=13.86÷4.2x=3.3
解:由题意得 4.2x=13.86 x=3.3