5586-5176=410. So they appeared to have closed 410 stores, which is 410/10=41 per year, on average.
(The revenue doesn't seem to have any bearing on what the question is asking for. It may have been inserted to confuse the puzzle-solver.
The difference in revenue is $1.1 billion. On average each lost store's revenue was $2.683 million.
$8.9 billion from 5586 stores averages to $1.593 million per store, and $7.8 billion from 5176 stores averages to $1.507 million per store. The drop in average revenue is due to the loss of 410 stores that had a higher average revenue.)