3 - (1/2 + 1/7) = 2 5/14
1) 1/2 + 1/7 = 7/14 + 2/14 = 9/14
2) 3 - 9/14 = 2 14/14 - 9/14 = 2 5/14
2 - (11/19 + 15/38) = 1 1/38
1) 11/19 + 15/38 = 22/38 + 15/38 = 37/38
2) 2 - 37/38 = 1 38/38 - 37/38 = 1 1/38
7 - (19/40 + 1/3) = 6 23/120
1) 19/40 + 1/3 = 57/120 + 40/120 = 97/120
2) 7 - 97/120 = 6 120/120 - 97/120 = 6 23/120