5.3x-2.4x=18.56
2.9X=18.56
X=6.4
3.7x-x=1.62
2.7X=1.62
X=0.6
（x+18.3）x 2=67.8
2X+36.6=67.8
2X=67.8-36.6
2X=31.2
X=15.6
6x＋4x=731
10X=731
X=73.1