Imagine that you have a biased two-sided coin. However, while you know that the coin is biased, you are unsure as to how the coin is biased; that is, you do not know the probability of getting a head or tail.
The first challenge is to use the coin to make a binary decision that has a 50% probabilty. In other words, find a way to make a fair decision.
Imagine that you have a biased 6 six-sided die. As before, you have no idea how the die is biased.
The second challenge is to think of a method to somehow transform (via mathematical, non-physical-manipulation methods) the die into a fair die.
It may be neccessary to flip the coin more than once. Same goes for the die.
"May be" ==> "is".