3)
а) 3 13/45+6 17/45=148/45+287/45=435/45=87/9=29/3=9 2/3
б) 12 43/56-7 22/56=672/56-392/56= 280/56=40/8=5
4) 5/6 и 3/4 = 10/12 и 9/12
7/8 и 5/6= 21/24 и 20/24
5/28 и 9/14= 5/28 и 18/28
5) 3/4 ;5/12; 4/15; 7/20
3/4= 75/60
5/12= 20/60
4/15=16/60
7/20=21/60
4/15; 5/12;7/20;3/4