Выражение: 1) 2/5a+3/5a 2) 7/9a-5/9a 3)3/8c+3/8c 4)9/11b+4/11c+6/11c+5/11b 5)11/13d-(8/13d+4) 6)9/10n-(8/10n-3)

1) 2/5 a + 3/5 a = 5/5 a = a

2) 7/9 a - 5/9 a = 2/9 a

3) 3/8 c + 3/8 c = 6/8 c = 3/4 c

4) 9/11 b + 4/11 c + 6/11 c + 5/11 b = 14/11 b + 10/11 c = 1 целая 3/11 b + 10/11 c

5) 11/13 d - (8/13 d + 4) = 11/13 d - 8/13 d - 4 = 3/13 d - 4 = (3d - 52)/13

6) 9/10 n - (8/10 n - 3) = 9/10 n - 8/10 n + 3 = 1/10 n + 3 = (n+30)/10