Question 511422
The fundamental distance equation is d=rt.
The combined distance they travel is 68 miles.
They travel for the same amount of time, which we will call 't'.
One travels 10 miles/hr * t hours.
The other travels 7 miles/hr * t hours.

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10t + 7t = 68
17t = 68
t = 4
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Check to see how far they travel in 4 hours.
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10 miles/hr * 4 hr = 40 miles
7 miles/pr * 4 hr = 28 miles
40 miles + 28 miles = 68 miles
Correct.
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Answer:  The two cars will be 68 miles apart in 4 hours.
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Done.