3/5:7/11=3/5*11/7=-33/35
5/7:4/21=5/7*21/4=5/1*3/4=15/4=3,75
20/27:4=20/27*1/4=5/27*1/1=5/27
1 2/3:5/6=5/3*6/5=6/3=2
4 1/2:9/20=9/2*20/9=20/2=10
3 1/6+10=13 1/6
х+1/9х=1 7/18 1 7/18:1 1/9=25/18:10/9=25/18*9/10=5/2*1/2=5/4=1,25
1 1/9х=1 7/18
х=1 7/18:1 1/9
х=1,25