Вычислите дробей 3/5+1/5,2/7+1/3,3/4+5/12,2/25+1/20,3/7-2/7,11/12-2/3,2/3-5/9,5/21-3/14

3/5+1/5=4/5
2/7+1/3=6/21+7/21=13/21
3/4+5/12=9/12+5/12=14/12= 1 1/6
2/25+1/20=8/100+5/100=13/100
3/7-2/7=1/7
11/12-2/3=11/12-8/12=3/12=1/4
2/3-5/9=6/9-5/9=1/9
5/21-3/14=10/42-9/42=1/42