Выполните действия: а) 1/4+1/5 б) 1/3+1/7 в) 3/5+3/4 г) 1/2+7/9

1/4+1/5= 5/20 + 4/20 = 9/20
2) 1/3+ 1/7 = 7/21 + 3/21 = 10/21
3) 3/5 + 3/4 = 12/20 + 15/20 = 27/20
4) 1/2 + 7/9 = 8/18 + 14/18 = 22/18 = 11/9 = 1 целая 2/9

1/4+1/5=5/20+4/20=9/20
1/3+1/7=7/21+3/21=10/21
3/5+3/4=12/20+15/20=27/20=2 7/20
1/2+7/9=9/18+14/18=23/18=1 5/18