Answer:
[tex]k=2.5[/tex]
Step-by-step explanation:
[tex]y \propto x[/tex]
[tex]y=kx[/tex]
[tex]k[/tex] is the proportionality constant.
[tex]y=2.5x[/tex]
The [tex]y[/tex] is the independent variable and [tex]x[/tex] is the dependent variable.
The proportionality constant is [tex]2.5[/tex].