What is the mean of this set: {2, 6, 7, 9, 9, 9}?

To find the mean, add the numbers and divide by how many numbers there are. Their sum is 2 + 6 + 7 + 9 + 9 + 9 = 42, and there are 6 numbers. So the mean is 42 ÷ 6 = 7, which is choice B.

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