input: Write a function to add a given integer mark to each value in a list of marks. Return the modified list of marks.
  assert add_marks([87, 56, 99, 54], 4)==[91, 60, 103, 58]
  assert add_marks([90, 75, 88, 70], 5)==[95, 80, 93, 75]
  assert add_marks([65, 50, 85, 90], 0)==[65, 50, 85, 90]
  assert add_marks([], 10)==[]
  assert add_marks([100, 100, 100], 0)==[100, 100, 100]
output: def add_marks(marks, mark_to_add):
      return [mark + mark_to_add for mark in marks]