1) 21 7/9 - 1 4/7 = 21 49/63 - 1 28/63 = 20 21/63 = 20 3/9 = 20 1/3 ( га ) во второй день
2) 21 7/9 + 4 5/8 = 21 56/72 + 4 45/72 = 25 101/72 = 26 29/72 ( га ) в третий день
3) 21 7/9 + 20 1/3 + 26 29/72 = 21 7/9 + 20 3/9 + 26 29/72 = 41 10/9 + 26 29/72 = 42 1/9 + 26 29/72 = 42 8/72 + 26 29/72 = 68 37/72 ( га ) за три дня