1) 2 4/7:(0,5х-23/35)=7,5          7,5=7 1/2 ,а 0,5=1/2

0,5х-23/35=2 4/7: 7 1/2

1/2х-23/35=18/7*2/15

1/2х-23/35=36/105

1/2х=36/105+23/35

1/2х=36/105+69/105

1/2х=105/105 значит =1

х=1:1/2

х=1*2/1

х=2

3) (1/4+3/4х):0,45=25/36        0,45=45/100=9/20

   1/4-3/4х=25/36*9/20

1/4-3/4х=5/16

3/4х=5/16-1/4

3/4х=5/16-4/16

3/4х=1/16

х=1/16: 3/4

х=1/16*4/3

х=1/12

проверял все сошлось