SOLUTION: Stefan left home and drove west at an average speed of 21 mph. Some time later Shreya left driving in the same direction but at an average speed of 35 mph. After driving for 3 hour

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Question 998221: Stefan left home and drove west at an average speed of 21 mph. Some time later Shreya left driving in the same direction but at an average speed of 35 mph. After driving for 3 hours Shreya caught up with Stefan. Find the number of hours Stefan drove before Shreya caught up.
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
              speed        time       distance
Stefan        21           t+3          d
Shreya        35            3           d

Question asks for t. Note that both went the same distance upon their meeting.

system%2821%28t%2B3%29=d%2C35%2A3=d%29

21%28t%2B3%29=35%2A3

t%2B3=35%2A3%2F21

highlight%28t=35%2A3%2F21-3%29

highlight%28highlight%28t=2%29%29