To me it gives you all the information needed to anwser the question without using an x. the anwser would be Sally lives 4 miles away. that is because if you take jordan (17) and subtract 1 (because he lives 1 more then 4 times as far) (16) (now you have exactly 4 times as far as sally) and divide by 4 (that gives you where sally is) (4) that is the anwser for Sally.
