Question 1151660
Sean traveled 18 miles on a cross country skiing trip. The first part of the trip, he averaged 6 mph, but the second part contained some steep hills, and he averaged  only 4 mph. the total trip took 3.5 hours , how long did he ski on each part of the trip?
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d = 18 miles
d = 6*t + 4*(3.5 - t)
6t + 14 - 4t = 18
etc