X-7/12=5/9
x-7/12+7/12=5/9+7/12
x=41/36

7/10-x=2/3
7/10-x+x=2/3+x
7/10-2/3=2/3+x-2/3
1/30=x
x=1/30

x-4/7=1/5
x-4/7+4/7=1/5+4/7
x=27/35

12/11-x=1/7
12/11-x+x=1/7+x
12/11=1/7+x
12/11-1/7=1/7+x-1/7
73/77=x
x=73/77


2x+5/8=5/8
2x+5/8-5/8=5/8-5/8
2x=0
2x÷2=0÷2
x=0

x+7/18=5/6
x+7/18-7/18=5/6-7/18
x=4/9