1/4:(3/4х-1/4)+2/5=1/2
1/4:(3/4х-1/4)=1/2-2/5
1/4:(3/4х-1/4)=5/10-4/10
1/4:(3/4х-1/4)=1/10
3/4х-1/4=1/4:1/10
3/4х-1/4=10/4
3/4х=10/4+1/4
3/4х=11/4
х=11/4:3/4
х=11/3
х=3 2/3
Если в знаменателе -1/2, то:
1/4:(3/4х-1/2)+2/5=1/2
1/4:(3/4х-1/2)=1/2-2/5
1/4:(3/4х-1/2)=5/10-4/10
1/4:(3/4х-1/2)=1/10
3/4х-1/2=1/4:1/10
3/4х-1/2=5/2
3/4х=5/2+1/2
3/4х=6/2 =>3
х=3:3/4
х=4