Answer:
They both attempted to preserve the Union.
Step-by-step explanation:
What the Missouri Compromise (Compromise of 1820) and the Compromise of 1850 had in common is that "They both attempted to preserve the Union."
This is evident in the fact that both Compromises seeks to preserve the Union by appealing to both pro-slavery and anti-slavery groups in government, by ensuring there is a balance between t slave states and free states.
Therefore, it can be concluded that both Compromise "attempted to preserve the Union."