вычислить 5/12:(1/3*2,5-7/8)-1,25

 5/12:(1/3*2,5-7/8)-1,25 = -11.25
1.  1/3*2.5=1/3*25/10 = 25/30 = 5/6
2.  5/6 - 7/8 = 20/24 - 21/24 = -1/24
3.  5/12 : (-1/24) = -(5/12*24/1) = -120/120=-10
4.  -10 - 1.25 = -11.25