Question

A recipe for chocolate chip cookies used 3 cups flour and sticks 2 sticks of butter is the amount of butter used proportional to the number of cups of flour used.

Answer 1

I believe so. 
Because if we make x flour, and y butter. 
If you doubled or tripled the recipe the x and y would have to increase. And every time x increases y will also have to increase. 

I hope this helps you.