They are asking how you get (Y). So, the first one says Y=9.2x-2.1. times 9.2 by x. which in this case x=2. 9.2*2=18.4. 18.4-2.1=16.3. does not equal y which is 15. so then you move to the next one Y=9x-3. 9*2=18. 18-3=15. But you have to go down the Line to see if it works for every number. But non of them match every number. so i am not sure. But that is how u find out. The closets one would be the second one. Y=9x-3.
~Hope this helped~