If Hailey increased her points by 20%, she would score 18 points this week. Therefore, what we need to do is to multiply 15 by 0.20. How did we get 0.20? Well, we divided 20 by 100 to get 0.20. Anyway, once we have multiplied 15 by 0.20, we get 3. However, this answer would not be logical because she increased her points by 20% - we are going up and not down. So, we add 15 and 3 together to get a total of 18 points scored.