the three major west african empires increased their wealth by\no trading gold and precious jewels.\no…

Brief Explanations:

The three major West - African empires (Ghana, Mali, Songhai) grew wealthy mainly by taxing all trade in their regions. They controlled important trade routes and levied taxes on goods passing through, which was a significant source of revenue. Trading gold and jewels was part of the trade but not the main way to increase wealth. Restricting trade to high - level merchants was not the key factor for wealth growth. Pooling trade earnings into one central account was not how they increased wealth.

Answer:

taxing all trade in their region.