How can we balance representation in government between free states and slave states

There are several aspects of American history that explain the relative balance between states that abolished slavery and those that retained it during much of the time between the ratification of the Constitution and the Civil War. Various compromises allowed new states to enter the Union after the original thirteen in order to keep the balance. The maintenance of the balance was tied to the Constitution and how the document organized Congress. While a balance was maintained for much of the antebellum period, the various compromises conceded much to the South. The delicate balance eventually crumbled and led to the Civil War.

The answer would have to be -16