4,1/12 - 3,7/8 = 8,2/24 - 11.1/24 = -2,9/24 3,11/18:13/18 = 3,11/13 3,11/13 -2,9/24= (3,11*24 - 2,9*13)/24*13 = (74,64 - 37,7)/312 = 36,94/312 = 1847/15600