28 2/21 - (14 17/21 + 11 8/21)

First, add the fractions inside the parentheses:

14 17/21 + 11 8/21 = 25 25/21 = 26 4/21

Now, subtract the result from the original expression:

28 2/21 - 26 4/21 = 1 22/21

Therefore, the expression simplifies to 1 22/21.