Question

What is the constant of proportionality represented in the graph?

Answer 1

This constant of proportionality is equal to the slope of the line

If we asume each rectangle side is equal to a unit, then

Point 1 (0,3)
Point 2 (5,-1)

m = (y2 - y1) / (x2-x1)

m = (-1 - 3) / (5-0)

m = (-4) / (5) = -4/5 = k