120％x－十二分之十一x＝6.5
6/5 x - 11/12 x = 6.5
17/60 x = 6.5
x = 6.5×60/17 = 22.9
4x＋0.4x=70.4
4.4x = 70.4
x=70.4/4.4 = 16
3x＋90％×4＝9
3x = 9-3.6
x=5.4/3 = 1.8