answer
$962.50
set up equation
first, we want to find out how many gallons of gas she'll save a year
x1 = gallons for old car
x2 = gallons for new car
gallons saved = x1 - x2 since she uses more gallons with the old car with a lower miles per gallon
then, find how much she saves on gas by multiply the price per gallon (3.85) by gallons saved
price saved = gallons saved * price
price saved = (x1 - x2) * 3.85
gallons with old car
to find the number of gallons, we divide the number of miles (15000) by miles per gallon (24 for the old car)
x1 = 15000 / 24
x1 = 625
gallons with new car
use the same process as with the old car, but with 40 miles per gallon instead
x2 = 15000 / 40
x2 = 375
plug in values
price saved = (x1 - x2) * 3.85
price saved = (625 - 375) * 3.85
price saved = 250 * 3.85
price saved = $962.50
