If there are three numbers the median has to be the middle number so the numbers are x,7,y. The three numbers must add up to 3×3 which is 9. Y must be larger than 7 so lets say that it's 8. 7+8=15 so x must equal -6. The difference between x and y is the range so the range is 8--6 which equals 14. The range is 14
