My problem says that 1 out of 2 people in the neighborhood have a car. How many people out of 100 neighbors have a car? I don't understand what that means. First they say 2 people then 100...
If out of $2$ neighbors you have $1$ neighbor that owns a car, then out of $100$ neighbors there are $50$ neighbors with a car. The statement of the question states that the ratio of "neighbors with a car" with respect to "neighbors" is a half. Therefore, to know how many neighbors out of $100$ have a car, you compute "half of $100$".
Hope that helps,