To solve the expression 2/3 + 7/9 - 5/11, we need to find a common denominator for the fractions. The least common denominator (LCD) for 3, 9, and 11 is 99.

Converting the fractions to have a denominator of 99:
(2/3) * (33/33) = 66/99
(7/9) * (11/11) = 77/99
(5/11) * (9/9) = 45/99

Now we can add the fractions:
66/99 + 77/99 - 45/99 = (66 + 77 - 45)/99 = 98/99

Therefore, 2/3 + 7/9 - 5/11 equals 98/99.

To solve the expression 2/7 : 3/9 - 1/3, we need to divide 2/7 by 3/9 and then subtract 1/3.

Dividing 2/7 by 3/9:
(2/7) ÷ (3/9) = (2/7) * (9/3) = (2/7) * (3/1) = 6/7

Now we can subtract 1/3 from 6/7:
6/7 - 1/3

To subtract fractions, we need a common denominator. The least common denominator (LCD) for 7 and 3 is 21.

Converting the fractions to have a denominator of 21:
(6/7) * (3/3) = 18/21
(1/3) * (7/7) = 7/21

Now we can subtract the fractions:
18/21 - 7/21 = (18 - 7)/21 = 11/21

Therefore, 2/7 : 3/9 - 1/3 equals 11/21.