Вычислите: 5/11+1/11, 3/7+1/4, 3/5+2/15, 3/25+2/15, 3/5-2/5, 7/12-3/4, 5/8-5/9, 5/21-3/28

5/11+1/11=6/11;
3/7+1/4=12/28+7/28=19/28;
3/5+2/15=9/15+2/15=11/15
3/25+2/15=9/75+10/75=19/75
3/5-2/5=1/5
7/12-3/4=7/12-9/12=(-2/12)=(-1/6)
5/8-5/9=45/72-40/72=5/72
5/21-3/28=20/84-9/84=11/84