What percentage of each house of congress must approve a proposed constitutional amendment for it to be considered for ratification?

two-thirds

Explanation:

While there are two ways, only one has ever been used. All 27 Amendments have been ratified after two-thirds of the House and Senate approve of the proposal and send it to the states for a vote. Then, three-fourths of the states must affirm the proposed Amendment.

b) a state law could be declared illegal if it contradicted the constitution.

explanation:

the conflict of this case originated when james w. mcculloch, a cashier of the baltimore branch of the second bank of the united states that the congress had chartered in 1816, refused to pay a tax imposed by the maryland state.

in the case, the state of maryland appealed that the establishment of a second bank was unconstitutional since the constitution didn't say anything about granting that power to congress. however, the case determined that even if such right wasn't specifically stated in the constitution, it was part of the "implied powers" of the government enunciated in article i, section 8.

the case also eliminated maryland's legislation to impose taxes to a national bank, asserting that even though the states retained the power of taxation, the constitution's laws are supreme and can not be controlled by the states, therefore, if a state law contradicts the constitution, it should be declared illegal.

explanation: