Answer:
4
Explanation:
Constant of proportionality is the same as slope in the context of a linear function, which is defined as Δy / Δx. We can find this by taking two points and finding the difference in their x- and y-coordinates.
I'll use (1, 4) and (2, 8).
![\textrm{slope}=(8-4)/(2-1) = (4)/(1) = 4](https://img.qammunity.org/2023/formulas/mathematics/high-school/kqhextvynsmbyxszb5o56ydydy6bdfnf9r.png)