The mean is found by dividing the sum of all terms by the number of terms present in the set.
Set up the equation:

The mean of this sequence is
5.
15+17+12= 44
The sold 44 magazine subscriptions in total.
I think A would be your best answer or C because of the down hill slope. Also I would check with your teacher
Answer:
1/a^2 is the answer to this question