(1 - 7/15 + 0,4) : (8,3 + 4/19 - 15/38) = 19/257
1 - 7/15 + 0,4 = 1 - 7/15 + 2/5 = 1 - 7/15 + 6/15 = 3/15+6/15 = 9/15 = 3/5
4/19 - 15/38 = 8/38 - 15/38 = - 7/38
8 3/10 - 7/38 = 8 57/190 - 35/190 = 8 22/190 = 8 11/95
3/5: 8 11/95 = 3/5 : 771/95 = 3/5*95/771= 19/257