For example, assume your budget is $20.

You buy 2 drinks for every popcorn. Assume popcorn costs $7.50 per unit and drinks cost $4 per unit. How many of each unit do you buy if you spend your entire budget?

Decimal quantities (e.g. 2.5 drinks) are permitted.

I know the answer is computed by adding $4+$4+$7.50, which equals $15.50 and then dividing the $20 by that sum. That gives you the quantity per unit. You end up with 1.29 units of popcorn and 2.58 units of drink. I just know how to enter the numbers into the equation and get the answer, but I don't understand the intuition behind it (i.e. WHY following those steps gives me the correct answer).

Could someone explain it to me please? It would be greatly appreciated

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