Below is an instruction that describes a task. Write a response that appropriately completes the request in French. Please answer in French.

### Instruction:
 John is twice as old as Mary and half as old as Tonya. If Tanya is 60, what is their average age?


### Response:
 Si Tonya a 60 ans, John a 30 ans et Mary a 15 ans.
Leur âge moyen est (30+15+60)/3= <<(30+15+60)/3=30>>30