Write double(n) that returns n * 2, and double_sum(a, b) that returns double(a) + double(b) by calling double.
double_sum(2, 3) → 10
double_sum(0, 0) → 0
Submit runs 4 tests, including hidden edge cases.
Each hint gives a little more help. Try on your own first.
Run your code to see the output here.