-1 7/8*(12,2-10 2/3):1/4+15= 26 1/2
12,2-10 2/3 = 12 2/10 - 10 2/3 = 12 1/5 - 10 2/3 = 12 3/15 - 10 10/15 = 11 18/15 - -10 10/15 = 1 8/15
-1 7/8 : 1/4 = -15/8*4/1 = -15/2 =- 7 1/2
- 7 1/2* 1 8/15 = - 15/2* 23/15 = - 23/2 = 11 1/2
11 1/2 + 15 = 26 1/2