Final answer:
To find the common difference of the arithmetic sequence 7, 0, -7, ..., subtract consecutive terms to see that the common difference is -7.
Step-by-step explanation:
The student is asking to find the common difference of the arithmetic sequence 7, 0, -7, ... The common difference in an arithmetic sequence is the constant amount by which each term differs from its previous term. In this sequence, we can calculate the common difference by subtracting the second term from the first term or the third term from the second term. Doing this, we have 0 - 7 = -7 and -7 - 0 = -7. Thus, the common difference is -7.