A large downtown hotel consists of twenty-four levels. There is a ground level referred to as "the first floor", twenty-one above the ground levels (second floor, third floor, etc.) and two underground levels reserved for underground parking. The first level below ground level is Parking A, and the second level below ground level is labeled Parking B. Use the provided horizontal number line to help you answer the following questions. If each above ground level floor corresponds with its floor number on the number line, what number on the number line represents Parking A? [Type your answer as a number.]
