Lupe can ride her bike at a rate of 20 mph when there is no wind. On one particular day, she rode 2 miles against the wind and noticed that it took her the same amount of time as it did to ride 3 miles with the wind. How fast was the wind blowing that day?

Let the wind speed be w mph. Lupe’s speeds are 20 − w mph against the wind and 20 + w mph with the wind. Since the travel times are equal, 2/(20 − w) = 3/(20 + w); solving gives 40 + 2w = 60 − 3w, so w = 4. The wind was blowing at 4 mph.

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