To Toru По действиям: 1. 3 3/4 : 1,2 = 3 3/4 : 1 2/10 = 3 3/4 * 1 1/5 = 15/4 : 6/5 = 15/4 * 5/6 = 25/8 = 3 1/8 2. 3 1/8 - 4 = -(4 - 3 1/8) = -7/8 3. -7/8 * 1 1/7 = -7/8 * 8/7 = -1 4. - 1 - 3,9 = -4,9