Question 2 • Algebraic Reasoning
Because Marina takes the same time for both trips, set the biking time equal to the running time: 19.5/(r + 9) = 6/r, where r is her running speed. Cross-multiplying gives 19.5r = 6(r + 9), so 13.5r = 54 and r = 4. Marina runs at 4 mph, choice B.
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