**Given Information:**
- First term of the arithmetic progression (AP): a = 25
- nth term of the AP: -17
- Sum of the first n terms of the AP: S_n = 60

**Finding the Common Difference (d):**
To find the common difference (d) of an arithmetic progression, we can use the following formula:
nth term (T_n) = a + (n - 1)d, where n is the position of the term in the AP.

Let's find the value of n using the given information:
- First term (a) = 25
- nth term (T_n) = -17

Using the formula, we have:
- -17 = 25 + (n - 1)d

Simplifying the equation:
- -17 - 25 = (n - 1)d
- -42 = (n - 1)d

**Finding the Sum of the First n Terms (S_n):**
To find the sum of the first n terms of an arithmetic progression, we can use the following formula:
Sum of n terms (S_n) = (n/2)(2a + (n - 1)d)

Let's substitute the given values into the formula:
- S_n = 60
- First term (a) = 25

Using the formula, we have:
- 60 = (n/2)(2(25) + (n - 1)d)
- 60 = (n/2)(50 + (n - 1)d)

**Simplifying the Equation:**
Now, we have two equations:
1. -42 = (n - 1)d
2. 60 = (n/2)(50 + (n - 1)d)

We can solve these equations simultaneously to find the common difference (d).

**Solution:**
1. Rearrange the first equation:
- d = -42 / (n - 1)

2. Substitute the value of d in the second equation:
- 60 = (n/2)(50 + (n - 1)(-42 / (n - 1)))

Simplifying the equation further:
- 60 = (n/2)(50 - 42)
- 60 = (n/2)(8)
- 60 = 4n
- n = 15

3. Substitute the value of n back into the first equation:
- d = -42 / (15 - 1)
- d = -42 / 14
- d = -3

Therefore, the common difference (d) of the arithmetic progression is -3.

In summary, the common difference of the given arithmetic progression is -3.