(( 2/15:(1/5х-1/3))-1/12=1/24;
2/15:(1/5х-1/3)=1/24+1/12;
1/5х-1/3=2/15:1/8;
1/5х=2/15*8/1+1/3;
1/5х=16/15+1/3;
1/5х=16/15+5/15;
Х=21/15*5/1;
Х=21/3;
Х=7;
Проверка:
2/15:(7/5-1/3)-1/12=1/24;
2/15:(21/15-5/15)-1/12=1/24;
(2/15*15/16)-1/12=1/24;
1/8-1/12=1/24;
3/24-2/24=1/24;
1/24=1/24;