(8 7/15 - 3/4 + 4 2/5 - 8 7/25) : (4 1/4 - 2 3/4) = 2 13/30
1) 8 7/15 - 3/4 = 127/15 - 3/4 = (127*4 - 3*15)/60 = (508 - 45)/60 = 463/60 = 7 43/60
2) 7 43/60 + 4 2/5 = 463/60 + 22/5 = (463*1 + 22*12)/60 = (463 + 264)/60 = 727/60 = 12 7/60
3) 12 7/60 - 8 7/15 = 727/60 - 127/15 = (727*1 - 127*4)/60 = (727 - 508)/60 = 219/60 = 73/20 = 3 13/20
4) 4 1/4 - 2 3/4 = 17/4 - 11/4 = (17 - 11)/4 = 6/4 = 3/2 = 1 1/2
5) 3 13/20 :1 1/2 = 73/20 : 3/2 = 73/20 * 2/3 = 73/30 = 2 13/30