10. Modifying an element of a list in a function

I keep getting messages which are along the lines of this: Oops, try again. list_function([3, 3]) returned 6 instead of [3, 6]. Can someone please help me find the correct code?

```
def list_function(x):
key = x[1]+3
x[1] = key
return x[1]
n = [3, 5, 7]
list_function(n)
print n
```