Пошаговое объяснение:
1)2/9+7/11-10/99=691/1980;
1. 2/9+7/11=9/20;
2. 9/20-10/99=691/1980;
2) 3 5/12+9 1/6-5 1/18=7 19/36;
1. 3 5/12+9 1/6=12 7/12;
2. 12 7/12-5 1/18=7 19/36;
3) 18/85+6 5/63-7/18=5 3221/3570;
1. 18/85+6 5/63=6 1559/5355;
2. 6 1559/5355-7/18=5 3221/3570.
4) 5 2/8+11 7/12-5 1/18=11 8/2;
1. 5 2/8+11 7/12=16 9/20;
2. 16 9/20-5 1/18=11 8/2;
5) 9 2/5+3/8-4 3/20=5 5/8;
1. 9 2/5+3/8=9 31/40;
2. 9 31/40-4 3/20=5 5/8;
6) 10 1/12+2 5/36-2 7/72=10 1/8.
1. 10 1/12+2 5/36=12 2/9;
2. 12 2/9-2 7/72=10 1/8.