5x=25×4-15x
5x=100-15x
20x=100
x=5
7x-x+2×3=29.4
6x+6=29.4
6x=23.4
x=3.9
(28.8+5.5x+3.2)÷2=71
32+5.5x=142
5.5x=110
x=20
2x+1.3×7=20
2x+9.1=20
2x=10.9
x=5.45
3x-7×1.2=10.2
3x-8.4=10.2
3x=18.6
x=6.2
15×2-5x=23
30-5x=23
5x=7
x=1.4
105-28x=7×5
105-28x=35
28x=70
x=2.5