Final answer:
The percent tax a slave had to pay for his manumission varied in different societies and time periods.
Step-by-step explanation:
The percent tax a slave had to pay for his manumission varied depending on the specific circumstances and region. In Rome, enslaved individuals were often allowed to keep a portion of their earnings to buy their freedom. Additionally, enslaved women could earn their freedom after producing a certain number of children. Manumission was typically made official with a sum of money as well. It's important to note that manumission was not a universally applied practice and varied greatly in different societies and time periods.