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

### Instruction:
 如果我现在比比利大4倍，而比利4岁，那么比利出生时我多大？


### Response:
 我现在比利的年龄4倍，所以我现在16岁，因为比利4岁。
因此，当比利出生时，我12岁。