Question 16
A basket contains some apples. An takes out one third of them, then returns $15$ apples to the basket. Binh takes one third of the remaining apples, then returns $10$. The numbers of apples taken by An and Binh are equal. Chau also takes one third of the remaining apples, then returns $x$ apples. What is $x$ so that Chau takes the same number of apples as An and Binh?
