Question

international relations
the ancient muslim historian al - omari described mansa musa as \the most powerful, the richest, the most fortunate, the most feared by his enemies and the most able to do good for those around him\ in all of west africa.
how did mansa musa gain his fortune?
by forcing his subjects to convert to islam
by resisting conquest by the portuguese
by controlling the gold and salt trade
by conquering the city of timbuktu

Explanation:

Mansa Musa was the ruler of the Mali Empire. The Mali Empire was rich because it controlled the gold - salt trade routes in West Africa. Forcing subjects to convert to Islam was a religious aspect, not a source of fortune. The Portuguese conquest attempts were later and not relevant to Mansa Musa's fortune. While Timbuktu was an important city in the Mali Empire, it was the control of trade (gold and salt) that made Mansa Musa wealthy.

Answer:

by controlling the gold and salt trade