Answer :
Observing the relationship between x and y, we see that it is a linear relationship of the form
[tex]y=ax[/tex]To get a, let us divide a y value by its corresponding x value, we obtain,
[tex]\begin{gathered} a=\frac{3.9}{1.3}\text{ or}\frac{15}{5}=3 \\ a=3 \end{gathered}[/tex]Therefore the function equation for the input/output table is
y = 3x . Option C