6:5=x:75
5x=6*75
5x=450
x=90
5-x/4=3/7
(5-x)*7=4*3
35-7x=12
-7x=12-35
-7x=-23
x=23/7
x=3 2/7
y/0,6=25/3
3y=0,6*25
3y=15
y=15:3
y=5
x:1 7/50=5/57:1/2
1/2x=57/50*5/57
1/2x=1/10
x=1/10*2
x=1/5
7:8=y:96
8y=7*96
8y=672
y=672:8
y=84
2+y/5=4/9
(2+y)*9=5*4
18+9y=20
9y=20-18
9y=2
y=2/9
x/0,8=15/4
4x=0.8*15
4x=12
x=12:4
x=3
y:1 5/31=7 3/4:1/3
1/3y=36/31*31/4
1/3y=9
y=9*3
y=27
8:7=a:56
7a=8*56
7a=448
a=448:7
a=64