Question

For a weekend trip, you are average driving 35 miles per hour in the city and 60 miles per hour on the highway. If the 150 mike trip took 3 hours, how much of the time were you driving in the city

Answer 1

x      +y     =3         | -35
x*35+y*60=150
-35x -35y=-105
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/         25y=45
           y=45/25=9/5=1,8 hours
           x=3-1,8=1,2 hours
the answer is 1,2 hours