SOLUTION: Sue rode her bike 21 miles. She began traveling at 12mph, the slowed down to 8mph in a hilly section. The trip took 2 hours. How long was she traveling at 12 mph and how long at 8

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Question 1051201: Sue rode her bike 21 miles. She began traveling at 12mph, the slowed down to 8mph in a hilly section. The trip took 2 hours. How long was she traveling at 12 mph and how long at 8 mph?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
R%5B1%5D%2At%5B1%5D%2BR%5B2%5D%2At%5B2%5D=21
12t%5B1%5D%2B8t%5B2%5D=21
and
t%5B1%5D%2Bt%5B2%5D=2
t%5B1%5D=2-t%5B2%5D
Substituting,
12%282-t%5B2%5D%29%2B8t%5B2%5D=21
24-12t%5B2%5D%2B8t%5B2%5D=21
-4t%5B2%5D=-3
t%5B2%5D=3%2F4
and
t%5B1%5D=2-3%2F4
t%5B1%5D=5%2F4
45 minutes at 8 mph and 1 hr 15 min at 12 mph.