For task 2, they want you to only move 1 block. This means that only 2 of the pile will have a change in total sum. After adding all of them, we can see that 9 and 27 are the least and most respectively. Meaning you would need to change both of them to 18. The column that adds up to 9 needs another 9 to make 18 while 27 needs to get rid of 9 to make 18. Therefore, 9 from the 27 pile needs to move to the 9 pile.