The correct answer to this open question is the following.
Although there are no options either context or references, we can comment on the following.
Here you are probably talking about the Three-fifth Compromise, an agreement reached by the delegates that participated in the Constitutional Convention of 1787 in Philadelphia, Pennsylvania, to create the new Constitution of the United States.
Delegates from large and small states in the North and South reached an agreement during the works during the Convention. The proposal was made by delegate James Wilson.
Delegates agreed on the way slaves should be counted to determine the real population in the states. This was an important agreement because, in the end, this would the number of seats that each state would have in the lower chamber of Congress or the House of Representatives, and the number of taxes each state had to pay.
Finally, after many debates, the compromise was that they were going to count three-fifths of the state population of slaves toward the total population of the state. This allowed states from the South to have third more legislators in Congress and electoral because, in the beginning, slaves had been ignored.
