а) 7/12+х=3/4

х=3/4-7/12

х=9/12-7/12

х=2/12 = 1/6

б)5/8-х=1/12

х=5/8-1/12

х=15/24-2/24

х=13/24

в)х-5 7/11 = 8 7/22

х-46/11=78/22

х=46/11+78/22

х=92/22+78/22

х=170/22

х=7 16/22 = 7 8/11