1) 2/3:(4/9x-4/9)+1/20=4/5
2/3:(4/9x-4/9)=4/5-1/20
2/3:(4/9x-4/9)=3/4
4/9x-4/9=2/3:3/4
4/9x-4/9=8/9
4/9x=8/9+4/9
4/9x=4/3
x=4/3:4/9
x=3
5/7:(6/7x+3/7)-1/2=1/6
5/7:(6/7x+3/7)=1/6+1/2
5/7:(6/7x+3/7)=2/3
6/7x+3/7=5/7:2/3
6/7x+3/7=15/14
6/7x=15/14-3/7
6/7x=9/14
x=9/14:6/7
x=3/4
3/4:(5/8x-1/2)-1/8=1/4
3/4:(5/8x-1/2)=1/4+1/8
3/4:(5/8x-1/2)=3/8
5/8x-1/2=3/4:3/8
5/8x-1/2=2
5/8x=2+1/2
5/8x=2 1/2=5/2
x=5/2:5/8
x=4