Gas mileage is the number of miles you can drive on a gallon of gasoline. a test of a new car results in 535 miles on 21 gallons of gas. how far could you drive on 51 gallons of gas ? what is the car's gas mileage?

for finding the midpoint of any given 2 pair of points simply add the respective x coordinates with other x coordinate and the y coordinate with other y coordinate and divide them by 2

in your question it will be :

(3+1)/2 for the x coordinate of mid point i.e 2

[8+(-4)]/2 for the y coordinate of midpoint i.e 2

so coordinates of mid point of points (3,8) and (1,-4) will be (2,2)