Question 1056787
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Jessie recently drove to visit her parents who live 756 miles away. On her way there her average speed was 21 miles per hour faster 
than on her way home (she ran into some bad weather). If Jessie spent a total of 21 hours driving, find the two rates.
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Let x be the slower rate, in miles per hour (mph).
Then the faster rate is (x+21) mph.

Jessie spent {{{756/(x+21)}}} hours for the way "there".
She spent {{{756/x}}} hours for the returning trip.

The condition says

{{{756/(x+21) + 756/x}}} = 21.

Solve for x. For it, multiply both sides by x*(x+21). You will get

756x + 756*(x+21) = 21x*(x+1).

Divide both sides by 21. You will get

36x + 36(x+21) = x*(x+1).

Simplify and solve this quadratic equation.
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