Final answer:
Maria lives 480 miles away from the mountains.
Step-by-step explanation:
To find the distance between Maria's home and the mountains, we need to determine her average rate or speed. Let's call the distance between her home and the mountains 'd'. We can set up a formula using the average rate formula:
Average rate = distance / time
On the trip to the mountains, it took Maria 12 hours, so her average rate is d/12 miles per hour. On the trip back home, it took her 8 hours and she was driving 20 miles per hour faster, so her average rate is (d/8) + 20 miles per hour. Since the two average rates are equal, we can set up an equation:
d/12 = (d/8) + 20
Multiplying both sides of the equation by 24 (the least common multiple of 12 and 8) to eliminate the fractions, we get:
2d = 3d + 480
480 = d
Therefore, Maria lives 480 miles away from the mountains.