How did the Missouri compromise attempt to settle the issue over the spread of slavery?

i think this is the answer. drawing a line from Missouri's southern border, dividing free and slave portions across the rest of the Louisiana Purchase.

Explanation:

It helped settle the dispute of slave and free states. At the time Missouri applied for statehood, the states were 11 free 11 slave. So it was decided that all territory above 36 degree 30 latitude line with the exception of Missouri would would be free, all below slave

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