each inch is 115 miles, so if theres two inches theres double the amount that there would be if there was 1 inch, so if theres 7 inches then you would have 7 times the amount it would be if there was 1 inch, in this situation theres 7.5 so you would multiply the 115 miles by 7.5 becuase that's how many inches there is, so multiplying that is the same as adding 115 plus 115 plus 115, and so on till you get the amount you need. did this help?