(18 14/25 + 12 7/25) - (21 2/15 + 6 5/15) = 3 28/75,
1) 18 14/25 + 12 7/25 = 30 21/25,
2) 21 2/15 + 6 5/15 = 27 7/15,
3) 30 21/25 - 27 7/15 = 30 63/75 - 27 35/75 = 3 28/75
ну тип вот :')
