如何解方程?1.7.5x+2.5x=20 2.25.8-2x=12-7 3.4x+2.8=5.04 4.3x+2.3=6

7.5x+2.5x=20 25.8-2x=12-7 4x+2.8=5.04
10.5x=20 25.8-2x=5 4x=5.04-2.8
x=20*10.5 2x=25.8-5 4x=2.24
x=210 2x=20.8 x=2.24*4
x=20.8*2 x=0.56
x=10.4
3x+2.3=6.8 0.9x-4*1.3=1.1
3x=4.5 0.9x-5.2=1.1
x=4.5*3 0.9x=1.1+5.2
x=1.5 0.9x=6.3
x=6.3*0.9
x=7
1.3*7=25.1-8x 4.8+0.5x=6.3 (25+2x)*4=340
9.1=25.1-8x 0.5x=6.3-4.8 25+2x=340X4
25.1-9.1=8x 0.5x=1.5 25+2X=1360
16=8x x=1.5*0.5 2x=1360-25
16*8=x x=3 2x=1335
2=x x=1335*2
x=667.5