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

### Instruction:
 史蒂夫手里拿着镍币和一角硬币。他比镍币多4个一角硬币。他手里总共有70美分。他手里有多少个镍币？


### Response:
 设x为他手里的镍币数量
一角硬币的数量 = x+4
总美分数 = 5*x + 10*(x+4) = 70
5x + 10x + 40 = 70
15x = 30
x = 2，史蒂夫手里有2个镍币。