а) 2/7 + 3/7 = 5/7

б) 2/3 + 2/9 = 6/9 + 2/9 = 8/9

в) 3/5 + 37 = 3/5 + 37 * 5/5 = 3/5 + 185/5 = 188/5

г) 1/6 + 38 = 1/6 + 38 * 6/6 = 1/6 + 228/6 = 229/6