А)3/5 + 7/25 + 1/15 =(3* 15 +7 * 3+1 * 5)/75 = 45 /75 + 21 /75 + 5/75 = 71/75
б)1/6 + 11/18 + 23/24 =(1 * 12 + 11 * 4 + 23 * 3)/72 = 12/72 + 44/72 +69/72 = 125/72 = 1 53/72
в)13/51 + 1/3 + 2/17 =(13 * 1 + 1 * 17 + 2 * 3)/51 = 13 /51 + 17/51 + 6/51 = 36/51 = 12/17
г)1/44 + 1/11 + 9/22 =(1 * 1 + 1 * 4 + 9 * 2)/44 = 1/44 + 4/44 + 18/44 = 23/44