5,25 - (2 целых 3/11 * 7/9)+ 6 целых 8/11 :

5,25-(2 3/11 * 7/9)+6 8/11: 1 2/7- 1 1/8=
1) 2 3/11*7/9=154
2)6 8/11:1 2/7=154
3)5,25-154=-148,75
4)-148,75+74=-74,75
5)-74,75-1 1/8=-74 6/8-1 1/8=-75 7/8

1) 2 3/11 * 7/9 = 25/11 * 7/9 = 175/99 
2) 6 8/11 : 1 2/7 = 74/11 : 9/7 = 518/99 
3) 5,25 - ( 175/99 ) + ( 518/99 ) - 1 1/8 = 5 1/4 - 1 1/8 + ( 343/99 ) = 5 2/8 -
- 1 1/8 + ( 343/99 ) = 4 1/8 + 3 46/99 = 4 99/792 + 3 368/792 = 7 467/792 
Ответ 7 467/792