2/3:(4/9х-4/9)=4/5-1/20
2/3:(4/9х-4/9)=16/20-1/20
2/3:(4/9х-4/9)=15/20
2/3:(4/9х-4/9)=3/4
4/9х-4/9=2/3*4/3
4/9х=8/9+4/9
Х=12/9:4/9
Х=12/9*9/4
Х=3
5/7:(6/7х+3/7)-1/2=1/6
5/7:(6/7х+3/7)=1/6+1/2
5/7:(6/7х+3/7)=1/6+3/6
6/7х+3/7=5/7:4/6
6/7х+3/7=5/7*3/2
6/7х+3/7=15/14
6/7х=15/14-6/14
6/7х=9/14
Х=9/14*7/6
Х=3/4