Answer:15. It is a function16. It is a functionMapping diagram is attached for reference.Step-by-step explanation:Mapping diagram is a set of two parallel columns.The first column includes the 'domain'.And the second column includes the 'range'.A relation is a function,if every domain ([tex]x[/tex]) has only one range ([tex]y[/tex])The given coordinates in the set form are in the form ([tex]x,y[/tex])15. We observe that each '[tex]x[/tex]' is attached to only one '[tex]y[/tex]'Therefore this relation is a function.16. We observe that here also each '[tex]x[/tex]' is attached to only one '[tex]y[/tex]'Therefore this relation is also a function.