Answer:
(D) [tex]y=\frac{18}{6}x[/tex]
Step-by-step explanation:
We will be able to know if an equation has a constant of proportionality of 3 if the constant which is being multiplied by x is equal to 3.
[tex]\frac{8}{5} =1.6[/tex] so no for A.
[tex]\frac{1}{3} = 0.\overline{33}[/tex] so no for B too.
[tex]\frac{1}{4} = 0.25[/tex] so no for C as well.
[tex]\frac{18}{6} = 3[/tex], so D works.
Hope this helped!