Explanation: Since the car gets 27 mpg in the city and gets 35 mpg on the highway, you can set it up in the inequality 27 < < 35 and this represents the range a car can drive for 1 gallon, so to find the range for 3 gallons, you multiply this inequality by 3.
27(3)<<35(3) 27(3)=81 35(3)=105
Then you can insert the numbers into the inequality to get 81<<105.
Let the speed for the first 12 mi be x mi/h, the speed for 18 mi was (x+4) mi/h thus given that time=distance/speed the average time will be: 3=(12+18)/(x+x+4) 3=30/(2x+4) solving for x we get 3(2x+4)=30 6x+6=30 6x=24 x=4 mi/hr Answer: 12 mi/hr