A new fast food restaurant opened 5 months ago. The table belows shows the number of burgers they've sold so far.
Month | Burgers Sold |
1 | 3,171 |
2 | 2,068 |
3 | 1,840 |
4 | 3,511 |
5 | 2,508 |
| 13,098 |
The next month (after spending some money on an ad) they sold 10 times as many as they had sold in the previous 5 months. How many fewer burgers did they sell before running the ad than they did after running it?