Just count separately.

The first purchase price is 8 yuan, the retail price is 9 yuan, and the profit is 9-8 = 1 yuan.

Second purchase price 10 yuan, retail price 1 1 yuan, profit1-10 =1yuan.

The two profits * * * are 1+ 1 = 2 yuan.

What's there to argue about?

Elementary school math problem, earn 2 yuan.

The rule of two is an even number.

The rule of 3 is that the sum of all numbers is a multiple of 3, for example, 93,9+3 = 12,12 is a multiple of 3.

The rule of 5 is that the single digit is 0 or 5.

I don't know the rest.

40 cups

Suppose you only have 1 yuan on you now. You buy a cup with one yuan, and then you get a cup from the boss. You can calculate the money later. Now you are the money boss.

Then you have two cups now. Take them to the boss.

Two cups for one cup 1 cup = 1 yuan, so you don't owe the boss money.

So 1 yuan can buy 2 cups.

20 yuan can buy 40 cups.

40 is the correct solution.

20 cups+10 cup +5 cups +2 cups (one more empty cup)+1 cup (two empty cups add up)+1 cup (a passerby borrowed an empty cup and returned it to him after drinking).

=40