Answer:
550 gallons
Step-by-step explanation:
Karla used 12000/15 = 800 gallons to drive 12000 miles. (12000÷15=800)
Had she driven the hybrid, she would have used 12000/48 = 250 gallons. (12000÷48=250)
Therefore, she would have saved 800 − 250 = 550 gallons.