input: Write a function to calculate the average score from a list of scores.
  assert calculate_average([72, 84, 85, 90]) == 82.50
  assert calculate_average([50, 60, 70, 80, 90, 100]) == 75.00
  assert calculate_average([100, 95, 85]) == 93.33
output: def calculate_average(scores):
      return round(sum(scores) / len(scores), 2)