4/5 : 3/13 =
4/9 : 16/45=
6 10/13 : 1 5/39 =
55: 11/12 =
18/19:6=

4/5:3/13=4/5•13/3=52/15=3 7/15;4/9:16/45=4/9•45/16=20/16=10/8=5/4=1 1/4;6 10/13:1 5/39=88/13•39/44=2•3=618/19:6=18/19•1/6=3/19;