Aball weighs 15lb on earth and 5.7 pounds on mars. what is the constant proportionality between weight of an object on mars and earh?

So its asking you to find the gravity on earth relative to the gravity on mars.

Set up an equation to figure out the difference between the two gravities 


x=.38

I don't know what constant of proportionality is in this context but a ball on mars would weigh .38 the amount that it does on earth.