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

First, let's simplify the expression inside the parentheses:
3/8 + 5^2/ -24 = 3/8 + 25/ -24

Next, let's find a common denominator for the fractions:
The common denominator for 8 and -24 is 24.

Now, let's rewrite the fractions with the common denominator:
3/8 + 25/ -24 = (3 * 3)/(8 * 3) + (25 * -1)/(24 * -1)
= 9/24 - 25/24

Now, let's combine the fractions:
9/24 - 25/24 = (9 - 25)/24
= -16/24

Finally, let's simplify the expression outside the parentheses:
1 - 5/17 = (17 * 1 - 5)/17
= (17 - 5)/17
= 12/17

Now, let's multiply the results inside and outside the parentheses:
(12/17) * (-16/24) = (12 * -16)/(17 * 24)
= -192/408
= -8/17

Therefore, the value of a) is -8/17.

b) Let's simplify the expression inside the parentheses first:
79/67 - 28/41 = (79 * 41)/(67 * 41) - (28 * 67)/(41 * 67)
= (79 * 41 - 28 * 67)/(67 * 41)

Now, let's simplify the expression outside the parentheses:
1/3 + 12/67 + 13/41 = (41 * 1 + 12 * 41 + 13 * 3)/(3 * 41)

Now, let's subtract the expression inside the parentheses from the expression outside the parentheses:
(41 * 1 + 12 * 41 + 13 * 3)/(3 * 41) - (79 * 41 - 28 * 67)/(67 * 41)

To simplify this expression further, we need to find a common denominator for the fractions.

c) The expression G = 1/25 x 27 + 1/27 x 29 + 1/ 29 x 31 + ... 1/73 x 75 represents a series of fractions. To find the value of G, we need to find the sum of these fractions.