№ 544.
а) 1 3/7 + 2 5/7 + 1 2/7 + 3 6/7 = (1 + 2 + 1 + 3) + (3/7 + 5/7 + 2/7 + 6/7) = 7 + 16/7 = 7 + 2 + 2/7 = 9 2/7
б) 2 2/9 + 1 5/9 + 3 7/9 + 1 4/9 = (2 + 1 + 3 + 1) + (2/9 + 5/9 + 7/9 + 4/9 = 7 + 18/9 = 7 + 2 = 9
в) 3 2/5 + 1 4/5 + 2 3/5 + 1 3/5 = (3 + 1 + 2 + 1) + (2/5 + 4/5 + 3/5 + 3/5) = 7 + 12/5 = 7 + 2 + 2/5 = 9 2/5
г) 1 7/10 + 3 3/10 + 2 9/10 + 1 1/10 = (1 + 3 + 2 + 1) + (7/10 + 3/10 + 9/10 + 1/10) = 7 + 20/10 = 7 + 2 = 9