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