Carter wants to stop every 2 hours to stretch his legs, which means he will have 14 / 2 = 7 leg-stretching stops.
He also wants to make x additional stops for food and 3 additional stops for gas, so he will have x + 3 additional stops.
Each pit stop takes 20 minutes, so the total time spent on pit stops is (7 + x + 3) * 20 minutes.
To convert this to hours, we divide by 60: (7 + x + 3) * 20 / 60 hours.
The total time for the road trip, including pit stops, is 14 hours + (7 + x + 3) * 20 / 60 hours.
We are given that the total time for the road trip is 18 hours, so we can write: 14 + (7 + x + 3) * 20 / 60 = 18.
Simplifying the left side, we get: 14 + (10 + x) * 20 / 60 = 18.
Multiplying both sides by 60, we get: 840 + (10 + x) * 20 = 1080.
Expanding and simplifying, we get: 840 + 200 + 20x = 1080.
Combining like terms, we get: 1040 + 20x = 1080.
Subtracting 1040 from both sides, we get: 20x = 40.
Dividing both sides by 20, we get: x = 2.
The value of x is 2.
#### 2
The answer is: 2
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Carter has a 14-hour road trip.  He wants to stop every 2 hours to stretch his legs.  He also wants to make x additional stops for food and 3 additional stops for gas.  If each pit stop takes 20 minutes, how many hours will his road trip become?
If we know the answer to the above question is 18, what is the value of unknown variable x?

### Answer:
