



 
Hi Shanda. If the gap between them starts at 420 miles and 5 hours later it is zero, then the gap is shrinking at a rate of 420/5 = 84 mph. Since they are moving towards each other, both of their speeds are contributing to this gapclosing speed, so And the difference of their speeds is given to you: Use these two equations to find the answer to your question. Cheers,  


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