(x-3)÷2=7.5
x-3=15
x=18

13.2x+9x=33.3
22.2x=33.3
x=1.5

8x-3x=105
5x=105
x=21

5.4x+x=12.8
6.4x=12.8
x=2

x-0.36x=11
0.64x=11
x=17.1875