Answer:
6
Step-by-step explanation:
In order to find the common difference of the arithmetic sequence, we need to subtract the 2nd number to the 1st number so if we pick 2 pairs of numbers, we always get 6
Pairs of numbers: 1 and 7, 7 and 13, 13 and 19
7 - 1 = 6
13 - 7 = 6
19 - 13 = 6
