SOLUTION: Teresa drove to the mountains last weekend. There was heavy traffic on the way there and the trip took 12 hours . When Teresa drove home, there was no traffic and the trip only

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Question 1001641: Teresa drove to the mountains last weekend. There was heavy traffic on the way there and the trip took 12 hours . When Teresa drove home, there was no traffic and the trip only Took eight hours. If her average rate was 20 mph faster on the trip home how far away does Teresa Live from the mountains?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Basic uniform rates for travel, RT=D to relate rate, time, distance. 
            rate         time      distance
TO           r            12        d
FROM         r+20          8        d

system%28r%2A12=d%2C%28r%2B20%29%2A8=d%29

Two equations in two unknown variables, but you want a value result for d, the distance.

r=d%2F12
-
%28d%2F12%2B20%29%2A8=d
8d%2F12%2B160=d
8d%2B12%2A160=12d----do any computations later if practical
12%2A160=4d
12%2A40=d
highlight%28d=480%29