(8целых 3/4 -7целых 2/9)+(2.25-2целых 7/9)=

(8 3/4 -7 2/9)+(2.25-2 7/9)=1 1/18
1. 8 3/4-7 2/9=8 27/36-7 8/36=1 19/36
2. 2,25-2 7/9= 2 25/100-2 7/9=2 1/4- 2 7/9=2 9/36-2 28/36=- 17/36
3. 1 19/36+(-17/36)=1 19/36-17/36= 1 2/36=1 1/18