500
Ms. Melanie and Ms. Pat each drive a lot during their summer vacation. In the summer of 2016 Ms. Melanie actually drove 8,000 miles. Last summer Ms. Pat drove 630 miles and used 30 gallons of gas. Last summer Ms. Melanie drove 1,800 miles and used 36 gallons of gas. Which teacher's car uses less gas?
What is Ms. Pat (21 miles per gallon)?