B6

A.
Congress can propose an amendment by a 2/3 vote in each House.
State legislatures can ratify an amendment by a vote of 3/4 of the states.
B.
One informal method of changing the Constitution is Political practice, for example almost every member of Congress and every president since Washington has stated that they are a Democrat, Republican, Federalist or Whig. Another informal method is a result of changes in technology, for example proceedings of the Senate and House are on T.V. televisions influences our political agenda and guides our choice for candidates.
C.
Informal methods of changing the Constitution are used more often then formal methods because changing the Constitution takes a long time. If the public recognizes an issue that needs to be dealt with sooner rather than later, Congress won't put it through the long process of proposing and ratifying an amendment.