This amendment determines how the president and vice president are elected

Answer: 12th Amendment (Amendment XII)

Explanation:

12th amendment (Amendment XII) of Unit States of America Constitution determines the way the president and vice president will be elected, it gives room for the each elector to vote for president and vice president separately, as against the previous voting procedures which requires the elector to vote twice for the president only in the presidential election.

Before the twelfth amendment, each elector is entitled to cast two electoral votes during presidential election without separating the president vote from that of the vice president, after which the presidential candidate with the highest votes elected as president, and the candidate with the second highest votes elected as vice president.