Вычислите: а) 2 1/4 + 1 5/12 = б) 2 1/15- 1 2/5=

а) 2 1/4 + 1 5/12 = (2 * 4 + 1)/4 + (1 * 12 + 5)/12 = (8 + 1)/4 + (12 + 5)/12 = 9/4 + 17/12 = 9 * 3/12 + 17/12 = 27/12 + 17/12 = (27 + 17)/12 = 44/12 = 11/3;

б) 2 1/15 - 1 2/5 = (2 * 15 + 1)/15 - (1 * 5 + 2)/5 = 31/15 - 7/5 = 31/15 - 7 * 3/15 = 31/15 - 21/15 = (31 - 21)/15 = 10/15 = 2/3.