“Write a function sum_three() that accepts three values—not a sequence, but three arguments—and returns the sum of those three values. At the end of 6.3, Functions Have Scope, there is an example of a function, scoped(), that takes two arguments. Given this, you have already seen and typed in functions that accept zero, one, and two arguments, so now generalize to three.”

def sum_three(first, second, third):
    result = first + second + third
    return result

first = 1
second = 2
third = 3

sum_three(1, 1, 1)

3

sum_three(90, 6, 13)

109