To solve this expression, we need to follow the order of operations (PEMDAS).

First, let's calculate the subtraction inside the parentheses:
7/34 - 2 2/17 = 7/34 - 36/17
To subtract these fractions, we need to find a common denominator, which is 34.
7/34 - 36/17 = 7/34 - 68/34 = -61/34

Now, let's substitute this result back into the expression:
17/25 (-61/34) - (-1/2)
To multiply these fractions, we simply multiply the numerators and denominators:
(17 -61) / (25 * 34) - (-1/2)

-1037 / 850 - (-1/2)
To subtract these fractions, we need to find a common denominator, which is 850.
-1037 / 850 - (-425/850)
-1037 / 850 + 425 / 850 = -612 / 850

-612 / 850 = -306 / 425

Therefore, the final answer is -306 / 425.