Barter
There are many different things you can trade your Wii in for. You can trade this system in for another system or for money.
money
Bartering
they had a barter system. they didn't have money, just trade goods,
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Trade.
so at trade they can have a money everyone wants
A trade, an exchange, or barter. An economic system which operates without money is called a barter system.
The use of money increases economic efficiency because without it, we would be a barter system. In a barter system, if I want potatoes, and have oranges to trade, the person with the potatoes has to want oranges to be willing to trade with me. With the use of money, I can give him a known amount of value in money, which he can buy what he wants to with.
Barter is a system of trade where people exchange good or services without the involvement of money.
The capitalist system or "market economy" uses trade. You earn money where you want and use it to buy what you want (trading money for goods). It is possible that the question is looking for an answer of a "barter economy" where people trade goods and services directly without the use of currency (I give you 1 cow for 5 sheep).
Walras