Problem with the equation?

[blaeco]

I need to know why the equation is 2y-x >=0???
. a. Define the model (set of equations)
b. What is the maximum profit and the number of sodas and hotdogs ?. (Use a graphical solution ).

A man operates a pushcart. He sells hotdogs and sodas. His cart can support 210 lbs. A hotdog weighs 2 ounces, a soda weighs 8 ounces. He knows from experience that he must have at least 60 sodas and 80 hotdogs. He also knows that for every two hotdogs he sells, he needs at least one soda. Given he makes 8 Cents profit on a hotdog and 4 cents on a soda, find how many sodas and hotdogs he must have in order to maximize profits.
Maximize z = 0.8x + 0.4 y subject to
0.125x + 0.5y <= 210
1x >= 80
1y >= 60

-x + 2y >= 0 why this???????????????
if He also knows that for every two hotdogs he sells, he needs at least one soda, it should be 2x >=y

Thanks a lot