How can a bill can become a law without the presidents signature

If he specifically rejects the bill, called a veto, the bill returns to Congress. There it is voted on again, and if both houses of Congress pass the bill again, but this time by a two-thirds majority, then the bill becomes law without the President's signature.

what document? i can't tell you the answer unless i see the document.

the answer is federalism. hope this and good luck on your assignment!