Edward C. answered 03/27/15
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Caltech Grad for math tutoring: Algebra through Calculus
9C3 = 9! / ((9-3)!*3!) = 9*8*7 / 6 = 84
4*9C2 = 4 * 9! / ((9-2)!*2!) = 4 * 9*8/2 = 4 * 36 = 144