(15 5/6-9 25/27)-(2/3-5/18)+7/27+13/18=7 7/18
1)15 5/6- 9 25/27=95/6- 268/27=855/54-536/54=319/54=5 49/54
2) 2/3-5/18=12/18-5/18=7/18
3)5 49/54-7/18=319/54-7/18=319/54-21/54=298/54=149/27=5 14/27
4) 4 14/27+7/27=149/27+7/27=156/27=52/9=5 7/9
5) 5 7/9+13/18=52/9+13/18=104/18+13/18=117/18=6 9/18=6 1/2 или 6,5