Answer:
Ghana: Traded gold and expanded wealth through taxes. Berber nomads introduced Arabic and Islam.
Mali: Timbuktu was a center for trading, salt-gold trade, pilgrimage increased trade. Mansa Musa was Muslim, but he let people practice their own beliefs.
Songhai: Sunni Ali expanded the boarders, Askia Muhammad took control of the salt mines. Askia Muhammad spread Muslim through scholars because he believed that his previous ruler had not practiced Islam correctly.
Step-by-step explanation:
Not sure if this helps but found this on Quizlet.