Answer: 2.5
===============================================
Explanation:
Pick any point on the diagonal line, that isn't the origin, and divide the coordinates like so: k = y/x
For example, the point (x,y) = (100,250) leads to k = y/x = 250/100 = 2.5
Or you could pick (x,y) = (300,750) which leads to k = y/x = 750/300 = 2.5
Direct proportion equations are always in the form y = kx with k = y/x being the constant of proportionality.
