3.5x=0.28+2.1 ; 3.5X=2.38 ; X=2.38/3.5 ; X=0.68
解:3.5x=0.28+2.1=2.38,则x=0.68
解;3.5x -2.1 = 0.283.5x = 2.1 + 0.28x = 2.38 ÷ 3.5x = 0.68