Question 518179
d = r*t is the basic distance equation
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Car:
d = 105 miles
r = speed of motorcycle +8 = s+8
t = same as motorcycle = d/r = 105/(s+8)
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Motorcycle:
d = 93 miles
r = speed of motorcycle = s
t = same as the car = d/r = 93/s
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t = t
so
105/(s+8) = 93/s
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cross multiply
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105*s = (s+8)*93
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105s = 93s + 744
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12s = 744
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s = 62 mph = motorcyle's speed
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s + 8 = 70 mph = car's speed 
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Check the answer:
How long does it take the car to travel 105 miles?
105/70 = 3/2
How long does it take the motorcycle to travel 93 miles?
93/62 = 3/2
Correct.
.
Done.