your function should work for more then 1 list, functions that work for just a single list is not really great. Look:
n = [3, 5, 7]
for i in range(0, len(n)):
n[i] = n[i] * 2
# Don't forget to return your new list!
n[i] = x
your function should work for all this lists (and more) (the exercise also calls the function multiply times with different lists for validation purpose, that is where
[12,20,28] comes from)
to make your function work for all this lists you supply as arguments, use the function parameter (
x) inside the function instead of
(the argument you supply at function call, gets copied into the function parameter)
The great things about functions is that we can use them multiply times, by simply calling the function again and supplying a different argument.