I went to the bookshop and spent one-half of the money that was in my purse.
When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.
You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?