It takes 10 minutes to ride around your neighborhood. We already know that going around the neighborhood once and your block twice is 15 minutes, so you can get rid of the two blocks and one neighborhood. Then subtract 15 minutes from 55, which is 40. So now we know that it takes 40 minutes to go around the neighborhood 4 times. Devide, and you get that one lap around the neighborhood is 10 minutes. It's kinda hard to explain in words, but maybe the picture will help.
