Alysha’s average speed when walking home from the market was 5 mph, and it takes her 21 minutes longer than when she drives to the market. If she drives along the same route, at an average speed that is 8 times her average walking speed, how many minutes does it take her to drive home from the market?

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  3 minutes

Step-by-step explanation:

Let x represent Alysha's time to drive home from the market.

Speed and time are inversely proportional to each other (for the same distance), so we have ...

  (walking speed)(walking time) = (driving speed)(driving time)

  5(x +21) = (8·5)(x)

  x +21 = 8x . . . . . . . . . divide by 5

  21 = 7x . . . . . . . . subtract x

  3 = x . . . . . . .divide by 7

It takes Alysha 3 minutes to drive home from the market.