Question

The graph below represents the price of sending video messages using the services of a phone company. What is the constant of proportionality?

A graph is shown. The values on the x axis are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. The values on the y axis are 0, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240. Points are shown on ordered pairs 0, 0 and 2, 48 and 4, 96 and 6, 144 and 8, 192. These points are connected by a line. The label on the x axis is Video Messages Sent. The label on the y axis is Price in cents.

Answer 1

constant of proportionality?

they are saying that

y = k x
for your data, where "k" is the constant of proportionality

Answer 2

to find k, use an (x,y) pair that is on the line (but not 0,0)
and solve for k