Answer: it must be agreed upon by two-thirds of both houses of Congress
Explanation: For a constitution to be amended, it must be agreed upon by two-third of both houses of Congress. , An amendment, whether proposed by Congress or a national constitutional convention, must be ratified by either the legislatures of three-fourths of the states or State ratifying conventions in three-fourths of the states. There are two ways to propose amendments, two-thirds of both houses of Congress can vote to propose an amendment, or two-thirds of the state legislatures can ask Congress to call a national convention to propose amendments.