ANSWER
5040 ways
EXPLANATION
When she puts the first block, she has 7 blocks to choose from. Then, for the second block, she has 6 blocks to choose from - since one is already placed. For the third block, she has 5 options, and so on. Therefore, to arrange all 7 blocks in a row,
[tex]7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1=5040[/tex]
Hence, there are 5040 ways to arrange the 7 blocks.
