5x＋2x＝42
7x=42
x=6
15＋2x－3＝48
2x=48-15+3
2x=36
x=18
2x＋3x＋17＝37
5x=37-17
5x=20
x=4
6x－3x＝6÷5
3x=6/5
x=6/5*1/3
x=2/5
x=0.4
9x－2x＝1.4＋0.07
7x=1.47
x=0.21
7（2x－6）＝15.4
14x-42=15.4
14x=15.4+42
14x=57.4
x=4.1