Explain what the Thirteenth and Twenty-First Amendments had in common

What will be an ideal response?

An ideal response will:
1, Explain that the Thirteenth Amendment abolished slavery and the Twenty-First Amendment repealed Prohibition.
2, Note that amendments generally avoided social and economic policy, with three exceptions: abolishing slavery, instituting a federal income tax, and prohibiting alcohol. So both the Thirteenth and Twenty-First Amendments dealt with social issues.
3, Explain that slavery and taxation were mentioned in the Constitution, so these were not new areas. But the failure of Prohibition was seen as providing good reason for social policies to be left out of the Constitution, because social norms can change.