To solve this expression, we need to perform the operations within the parentheses first, and then distribute the coefficients outside the parentheses.

First, let's simplify the expressions within the parentheses:

1,8 - 1 1/4a = 1,8 - 5/4a = 4/2 + (8/2 - 5/4)a = 16/8 - 10/8a = 6/8 - 10/8a = (6 - 10a)/81,2 - 5/14a = 1,2 - 10/14a = 7/2 - 5/7a = (49/14 - 10/14a) = (49 - 10a)/14

Now, substitute the simplified expressions back into the original expression:
2/3(6 - 10a/8) - 2 1/3(7 - 10a/14)

Distribute the coefficients:
(2/3 6 - 2/3 10a/8) - (2 1 + 1/3 7 - 1/3 * 10a/14)

Simplify:
(4 - 5a/4) - (2 + 7/3 - 5a/21)
(4 - 5/4a) - (2 + 2 1/3 - 5/21a)
(4 - 5/4a) - (8/3 + 7/3 - 5/21a)

Combine like terms:
4 - 5/4a - 8/3 - 5/3a + 7/3 - 5/21a
4 - 8/3 + 7/3 - 5/4a - 5/3a - 5/21a
(12 - 8 + 7 - 15/3 - 20/3 - 5/21)a
(3 - 3)/3 - 5/21
0 - 1/7
= -1/7

Therefore, the final answer is -1/7.