1. (1 1/15 + 1 13/30) : 2 = (1 2/30 + 1 13/30) : 2 = 2 15/30 : 2 = 2 1/2 : 2 = 5/2 : 2 = 5/2 * 1/2 = 5/4 = 1 1/4
2. (5 7/12 - 3 3/4) : 3 = (5 7/12 - 3 9/12) : 3 = (4 19/12 - 3 9/12) : 3 = 1 10/12 : 3 = 1 5/6 : 3 = 11/6 : 3 = 11/6 * 1/3 = 11/18
3. (5 1/2 + 6 2/3 - 7 1/4) * 8 = (5 6/12 + 6 8/12 - 7 3/12) * 8 = (11 14/12 - 7 3/12) * 8 = 4 11/12 * 8 = 32 88/12 = 39 4/12 = 39 1/3
4. (2 2/3 - 5/9 + 1/3 + 3/7) * 21 = (2 4/9 - 5/9 + 3/9 + 3/7) * 21 = (2 2/9 + 3/7) * 21 = (2 14/63 + 27/63) * 21 = 2 41/63 * 21 = 44 861/63 = 57 42/63 = 57 2/3