2x+3x=10
5x=10
x=10/5
x=2
2.1x+1.4=35
2.1x=35-1.4
2.1x=33.6
x=33.6/2.1
x=16
7x减1.4x=1.28
5.6x=1.28
x=1.28/5.6
x=8/35