Mike had x pieces of candy. He kept pieces 15 for himself and equally divided the remaining pieces among his 6 friends. How many pieces of candy did each of his friends get?

each friend got (x-15)/6

9

To find out how many pieces of candy each of Mike's friends got, we need to subtract the number of pieces he kept for himself from the total number of candy pieces he had and then divide the remaining pieces equally among his friends.

Let's say Mike had x pieces of candy.
He kept 15 pieces for himself.
So, the remaining number of candy pieces is (x - 15).

Now, we need to divide the remaining pieces equally among his 6 friends. To do that, we divide the number of pieces of candy remaining by the number of friends.

Each friend will get ((x - 15) / 6) pieces of candy.

So, the number of candy pieces each of Mike's friends got is ((x - 15) / 6).

Are you supposed to write an algebraic expression? There is not enough information to determine a numeric answer.