Randy has 97 blocks. He uses some blocks to build a tower. If there are 72 blocks left how many blocks did he use to build the tower?
. 

Randy has 97 blocks. He uses some blocks to build a tower. 

That means that he has used some of his 97 blocks to build the tower. 

We can write this as:

97 - some number = 72

We want to solve for "some number." This is the number of blocks that Randy used to build the tower. 

We can solve this equation by subtracting 72 from both sides. 

This gives us:

97 - 72 = some number

25 = some number

Randy used 25 blocks to build the tower.