In an arithmetic sequence, the common difference is the difference between any two consecutive terms.
To find the common difference \( d \) for the given sequence:
-
Subtract the second term from the first term: \[ d = 18 - 25 = -7 \]
-
Verify by checking the difference between the next terms: \[ d = 11 - 18 = -7 \] \[ d = 4 - 11 = -7 \]
The common difference of the arithmetic sequence is \( \boxed{-7} \).