Answer:
The common difference is 7.
Explanation:
The common difference in the arithmetic sequence 7, 14, 21, 28, ... is 7. This is because in an arithmetic sequence, the difference between any two consecutive terms is constant. In this case, 14 - 7 = 7, 21 - 14 = 7, and 28 - 21 = 7. So, the common difference is 7.