How to find real numbers of a function

Take a point that is plotted and do X1 - X2 
                                                     
                                                      Y1- Y2
EX: (8,5) AND (3,7)
8-3=5

5-7=-2

(5,-2) WOULD BE YOUR ANSWER

Khalid and Sue's Height together is 126 Inches. The difference is 6 inches, so therefore you subtract 6 from the total getting you 120 Inches. You do this with all of the problems for example: The first one. Sue is 72 inches and Khalid is 54. Add them together and subtract them by 6 to get your final answer. Please DO NOT quote me on this lol. This is how I read the question. I think this is right but I am not absolutely 100% sure. Hope this helps.