Suppose you have several coloured balls.
Two of the balls are red, and have the letters B and E on them.
Two of the balls are green, and have the letters M and R on them.
Two of the balls are orange, and have the letters A and E on them.
What letters are on the blue-coloured balls?
Two of the balls are red, and have the letters B and E on them.
Two of the balls are green, and have the letters M and R on them.
Two of the balls are orange, and have the letters A and E on them.
What letters are on the blue-coloured balls?