Дроби. вычислите: 1) 25/28- 2/12; 2) 41/54-35/72; 3) 20/21-3/14; 4) 40/143+39/110; 5) 43/140+41/150; 6) 73/80-37/100;

25/28 - 2/12=25/28 - 1/6=75/84 - 14/84=61/84

41/54 - 35/72=164/216 - 105/216=59/216
(54=18*3, 72=18*4, общий знаменатель-=18*3*4=216)

20/21 - 3/14=40/42 - 9/42=31/42

40/143 - 39/110=4400/15730 - 5577/15730= - 1177/15730

43/140 - 41/150=645/2100 - 574/2100=71/2100

73/80 - 37/100=730/800 - 296/800=434/800=217/400