To solve this problem, we need to first convert all the mixed numbers into improper fractions.

2/7 + 3 1/4 = 2/7 + 13/4 = 8/28 + 91/28 = 99/28

11/14 + 18/28 = 22/28 + 18/28 = 40/28

Now we can subtract the two fractions:

99/28 - 40/28 = 59/28

Therefore, (2/7 + 3 1/4) - (11/14 + 18/28) = 59/28.