Final answer:
An amendment can be proposed by two-thirds of each house of Congress, or by a constitutional convention called by Congress at the request of two-thirds of state legislatures. Ratification of an amendment requires approval from three-fourths of the states, or three-fourths of state legislatures.
Step-by-step explanation:
An amendment can be proposed by two-thirds of each house of Congress. Amendments can also be proposed by a constitutional convention called by Congress at the request of two-thirds of state legislatures. Ratification of an amendment requires approval from three-fourths of the states. Amendments can also be ratified with the approval of three-fourths of state legislatures.