28/40-10/75=7/10-2/15=21/30-4/30=17/30;
12/27+14/21=84/189+126/189=210/189=70/63=1целая 7/63;
14/24-15/40=14/24-3/8=14/24-9/24=5/24;
5/9+1/6+3/4=20/36+6/36+27/36=53/36=1 целая 17/36;
2020/3+4/9+5/6=6/18+8/18+15/18=29/18=1целая 11/18;
1/4+1/5-3/10=5/20+4/20-6/20=3/20