7x+5x=120
(7+5)x=120
12x=120
12x÷12=120÷12
x=10
16x-7x=27
(16-7)x=27
9x=27
9x÷9=27÷9
x=3
4x-1.2=74
4x-1.2+1.2=74+1.2
4x=75.2
4x÷4=75.2÷4
x=18.8
3.8x-x=0.56
(3.8-1)x=0.56
2.8x=0.56
2.8x÷2.8=0.56÷2.8
x=0.2
x-0.85x=3
(1-0.85)x=3
0.15x=3
0.15x÷0.15=3÷0.15
x=20