21/7 + 3 9/8= 12 7/12+3 8/9-4 3/4 = 1 -9/19 5 -4/11 2 3/4 -1 7/12 7 1/4-4 5/8 пож

2 1/7+3 9/8=15/7+33/8=120/56+231/56=351/56=6 15/56
1-9/19=19/19--9/19=10/19
5-4/11=4 11/11-4/11=4 7/11
2 3/4-1 7/12=11/4-19/12=33/12-19/12=14/12=1 1/6
7 1/4-4 5/8=29/4-37/8=58/8-37/8=21/8=2 5/8
12 7/12+3 8/9-4 3/4=151/12+35/9-19/4=453/36+140/36-171/36=422/36=11 26/36=11 13/18

1. = 2 8/56+4 7/56= 6 15/56
2. =12 21/36+3 32/36-4 27/36= 11 26/36=11 13/18
3. =19/19-9/19=10/19
4. =4 11/11-4/11=4 7/11
5. =2 9/12-1 7/12=1 2/12 = 1 1/6
6. =7 2/8-4 5/8=6 10/8-4 5/8=2 5/8