Final answer:
Beth and her family had traveled 102 1/4 miles before their first stop for gas.
Step-by-step explanation:
To find out how many miles Beth and her family had traveled before their first stop for gas, we need to subtract the distances covered after the gas stop and after lunch from the total distance traveled in the day.
First, we subtract the distance covered after gas from the total distance: 372 miles - 65 1/4 miles = 306 3/4 miles.
Next, we divide the remaining distance by 3 to find the distance covered before lunch: 306 3/4 miles ÷ 3 = 102 1/4 miles.
Therefore, Beth and her family had traveled 102 1/4 miles before their first stop for gas.