Two-thirds of the class have brown eyes. Half of the students with brown eyes have black hair. If there are 6 students in the class with brown eyes and black hair, how many students are there in total?
Let's be accurate as possible. Think before you answer.
18
There are 6 * 2 = 12 students with brown eyes and hair of any color.

There are 12 * 3 / 2 = 18 students in total.

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The answer is 18