input: Write a python function to find the sum of the two smallest numbers out of three given numbers.
  assert two_smallest_nums(10, 5, 8) == 13
  assert two_smallest_nums(1, 2, 3) == 3
  assert two_smallest_nums(7, 15, 3) == 10
output: def two_smallest_nums(a, b, c):
      nums = [a, b, c]
      nums.sort()
      return nums[0] + nums[1]