Buy x cups of coke and y cups of milk tea.

Because the sentence "if 20 yuan just runs out" was deleted.

That is to say, 20 yuan can't be used up.

According to the meaning of the question.

2x+3y is less than or equal to 20.

X+y=8, which is less than or equal to 8 if someone can live without drinks.

When you think, Y equals 4, and 20 yuan just runs out.

So it can be 4 cups of milk tea and 4 cups of coke.

3 cups of milk tea and 5 cups of coke.

Milk tea 1 7 cups of cola

So there are three ways to buy the first question ~

the second question

exist

2x+3y is less than or equal to 20.

X+y=8, provided that

It is known that x is greater than or equal to 1 and y is greater than or equal to 2.

So there are 4 cups of milk tea and 4 cups of coke.

3 cups of milk tea and 5 cups of coke.

Milk tea 1 7 cups of cola (in this case, milk tea does not meet the requirements)

So there are two ways to buy.

4 cups of milk tea and 4 cups of coke.

3 cups of milk tea and 5 cups of coke.