7/15+7/12=(84+105)/180=189/180=1 1/20
7/9-5/12=(84-40)/108=44/108=11/27
5/21+5/28=(140+105)/588=245/588
11/42-5/28=(22-15)/84=7/84
7/15+7/12=(84+105)/180=189/180=1 1/20
7/9-5/12=(84-40)/108=44/108=11/27
5/21+5/28=(140+105)/588=245/588
11/42-5/28=(22-15)/84=7/84