What is the median of a set of 9 numbers, where the first 4 numbers are 10, 15, 20, and 25, and the remaining numbers form an arithmetic sequence with a common difference of 4?
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What is the rule for congruence of triangles?
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What is the equation of an ellipse with center at (h,k), major axis of length 2a, minor axis of length 2b, and vertical orientation?