If congress proposes a law does three-fourths of the states must ratify it or it will not become a law?

It is not a new law that Congress can propose that takes the ratification of three-fourth's of the states. It is the proposal of a constitutional amendment. If two-thirds of both houses of Congress vote to propose a particular constitutional amendment, at least three-fourths of the legislatures of the fifty states must vote to ratify the proposed amendment before it can become law. The proposal can be made by national convention also. See Sources and related links for more information.