3) (1/8 + 2/9 - 1/4) * 5 1/7 : (7/9 - 2/3 + 1/6) = (9+16-18)/72 * 36/7 : (14-12+3)/18 = 7/72 * 36/7 : 5/18 = 1/2 * 18/5 = 9/5 = 1 4/5
4) (10 3/4 - 12 : 1 1/5) * 4/9 + 2 1/6 + 3 1/4 : 5 1/5 = (10 3/4 - 12/1 : 6/5) * 4/9 + 13/6 + 13/4 : 26/5 = (10 3/4 - 12/1 * 5/6) * 4/9 + 13/6 + 13/4 * 5/26 = (10 3/4 - 10) * 4/9 + 13/6 + 5/8 = 3/4 * 4/9 + 13/6 + 5/8 = 1/3 + 13/6 + 5/8 = (8+52+15)/24 = 45/24 = 1 21/24 = 1 7/8