Question 174
In the first table, every row is an arithmetic progression with the same common difference, and every column is an arithmetic progression with the same common difference. The second table follows the same construction rule, but all except three entries have been erased. Find the entry marked with a star.
| 5 | 8 | 11 | 14 | 17 |
| :---: | :---: | :---: | :---: | :---: |
| 12 | 15 | 18 | 21 | 24 |
| 19 | 22 | 25 | 28 | 31 |
| 26 | 29 | 32 | 35 | 38 |
| 33 | 36 | 39 | 42 | 45 |
| | | 39 | | |
| --- | --- | --- | --- | --- |
| | | | | |
| | | | | 87 |
| 56 | | | | |
| | | | $\star$ | |
| 5 | 8 | 11 | 14 | 17 |
| :---: | :---: | :---: | :---: | :---: |
| 12 | 15 | 18 | 21 | 24 |
| 19 | 22 | 25 | 28 | 31 |
| 26 | 29 | 32 | 35 | 38 |
| 33 | 36 | 39 | 42 | 45 |
| | | 39 | | |
| --- | --- | --- | --- | --- |
| | | | | |
| | | | | 87 |
| 56 | | | | |
| | | | $\star$ | |