This task is from Tools for NC Teachers. Students explore tasks with multiplicative comparisons. This task is remixable. 

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Jose has a bowl of M&Ms.  He picks out all of the blue M&Ms first, because they are his favorite.  He then picks out all of the green M&Ms and eats them. The green M&Ms are his second favorite.  He ate 9 times as many blue M&Ms as green M&Ms.  How many blue and green M&Ms could have been in his bowl?

What other possibilities of green and blue M&Ms could Jose have in his bowl?

Show your thinking with a model and an equation with a symbol for the unknown.