4x+20=76
4x=76-20
4x=56
x=56÷4
x=14
3x-15=27
3x=27+15
3x=42
x=42÷3
x=14
7x-3乘5=55
7x-15=55
7x=55+15
7x=70
x=70÷7
x=10
7x+2=4.5
7x=4.5-2
7x=2.5
x=2.5÷7
x=5/14
4x-1.5x=22.5
(4-1.5)x=22.5
2.5x=22.5
x=22.5÷2.5
x=9
2(x-1.3)=8
x-1.3=8÷2
x-1.3=4
x=4+1.3
x=5.3
(x+3)除以2=6.5
x+3=6.5×2
x+3=13
x=13-3
x=10