How would the simultaneous admission og’f Missouri and Maine help

preserve the balance of free and slave states in the United States?

The simultaneous admission of Missouri as a slave state and Maine as a free state in 1820 helped preserve the balance of free and slave states in the United States by maintaining an equal number of free and slave states in the Senate. This was important because each state had an equal number of senators and the Senate was responsible for passing laws and confirming appointments. The compromise helped to address the issue of the expansion of slavery into new territories and allowed the United States to remain united for several more decades.