Question

what would have happened in 1818 if missouri had joined the union as a slave state?
no other territory would have been granted statehood.
the balance of power in congress would have shifted.
states in the north would have been forced to legalize slavery.
there still would have been fewer slave states than free states.

Explanation:

In 1818, the United States had an equal number of free and slave states. If Missouri (a territory at that time) had joined as a slave state, it would have disrupted the balance between free - state and slave - state representation in Congress. Each state had two senators, so adding a slave state would give slave - holding interests more power in the Senate.

Answer:

The balance of power in Congress would have shifted.