Spend it, save it and invest it
If you have money in the bank you get a certain percentage interest. If you borrow money you have to pay a certain percentage extra back. If you buy a product a percentage of the price is tax. When you earn money you pay a percentage in tax. The government knows what percentage of the population are unemployed.
When people are in debt! You can owe people so much money that you actually have a negative amount of money.
Grading papers or adding money
There are a countless number of ways people use 20. For example, they could be counting 20 nickles in a dollar.
counting money
Money!
savings
Solar hot water systems help people to save money in a variety of ways. They allow people to not use electricity or gas when heating up their water for showers.
Spend it, save it and invest it
Well there's a lot of ways to get money. You can use the two cheats, kaching (it gets you $1,000) or motherlode (it gets you $50,000). You could also just get a job, like normal people :p but most people use cheats to.
They didn't use money, but their slaves did.
by doing chores for other people
Two ways that people use leaves as a resource is by composting for gardens and mulch for landscaping.
some people use water to clean and to drink.
As a factory.
Yes, people in Sudan do use money. The currency of Sudan is the Sudanese Pound.