What is the variance of a dataset {1, 4, 7, 10, 13}?
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What is the probability of drawing two red cards from a standard deck of 52 cards, without replacement?
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The equation of an ellipse is (x-h)^2/a^2 + (y-k)^2/b^2 = 1. Find the characteristics of an ellipse with center (2,-3) and semi-major axis 5, semi-minor axis 3.