Question 1127766
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There are many different ways to set up and solve this problem.  I will show you a couple that I like best.  Perhaps other tutors will respond showing different methods.<br>
(1) Probably the usual algebraic method....<br>
Let x be Samantha's speed
Then x+20 = Anna's speed<br>
Anna drives for 3 hours to go the same distance Samantha goes in 4 hours:<br>
{{{3(x+20) = 4(x)}}}
{{{3x+60 = 4x}}}
{{{60 = x}}}<br>
Samantha's speed is x = 60 mph; Anna's is x+20 = 80 mph.<br>
(2) The ratio of their times is 3:4, because Anna takes 3 hours and Samantha takes 4 hours.  Since they are both driving the same distance, the ratio of their speeds is 4:3.<br>
If the ratio of their speeds is 4:3 and Anna's speed is 20 mph faster, then the two speeds are 80 and 60 mph.