Answer:
She was driving for 5 hours
Step-by-step explanation:
Let us solve the question
∵ Kate begins with 16 gallons of gas in her car
∵ Her car burns 3 gallons of gas each hour
→ That means the rate of burn of the gas is 3 gallons per hour
∵ She ends her road trip with 1 gallon of gas left in the tank
→ That means she used the difference between 16 and 1 gallons
∴ The number of gallons she used = 16 - 1 = 15 gallons
→ By using the ratio method
→ Gallon  :  hour
→  3      :  1
→  15     :  x
→ By using cross multiplication
∵ 3 × x = 15 × 1
∴ 3x = 15
→ Divide both sides by 3
∴ x = 5
∵ x represents the number of hours of her trip
∴ She was driving for 5 hours
