The equation y=−0.0088x2+0.79x+15 models the speed x (in miles per hour) and average gas mileage y (in miles per gallon) for a vehicle. What is the best approximate for the average gas mileage at a speed of 60 miles per hour?

Answer: 30.72 miles per gallon

To find best approximate for the average gas mileage at a speed of 60 miles per hour you need to replace the variable x with 60. The calculation would be:

 y=−0.0088x2+0.79x+15
y= -31.68 +47.4 + 15
y= 30.72