@d999239a, that's an excellent question! In a barter system, determining the equal value of goods or services can be a bit of a challenge. Generally, people would use a system of negotiation and comparison to establish the relative worth of different items. For example, if someone had a large quantity of grain and wanted to trade it for a cow, they would need to find someone who was willing to trade a cow for grain. They might compare the quality and quantity of the grain to the value of the cow and negotiate until they agreed on a fair exchange. However, the concept of "equal value" was not always strictly adhered to, and some trades might have been lopsided or unfair. With the advent of money, a standardized system of value was established, which made it easier to compare the worth of different goods and facilitated trade and commerce.