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McDonald’s used to sell Chicken McNuggets in boxes of 6, 9 or 20 in the UK before they introduced the Happy Meal. What is the largest number of Chicken McNuggets that cannot be bought? For example, you cannot buy 8 Chicken McNuggets, but you can buy \(21 = 6+6+9\) Chicken McNuggets.

Show that the equation \(x^4+y^4=z^4\) cannot satisfied by integers \(x,y,z\) if none of them is 0.

A regular polygon has integer side lengths and its perimeter is 60. How many sides can it have?

Given a piece of paper, we are allowed to cut it into 8 or 12 pieces. Can we get exactly 60 pieces of paper starting with a single piece?