Ken can do x sit-ups.
Nathan can do twice as many sit-ups as Ken, which means Nathan can do 2x sit-ups.
The combined number of sit-ups that Ken and Nathan can do is x + 2x = 3x.
Bob can do half the number of Ken and Nathan's combined sit-ups, which means Bob can do (1/2) * 3x = (3/2)x sit-ups.
We are given that Bob can do 10 more sit-ups than Ken, so we can write: (3/2)x - x = 10.
Simplifying the left side, we get: (1/2)x = 10.
Multiplying both sides by 2, we get: x = 20.
The value of x is 20.
#### 20
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Ken can do x sit-ups without stopping. Nathan can do twice as many, and Bob can do half the number of Ken and Nathan's combined sit-ups. How many more sit-ups can Bob do compared to Ken?
If we know the answer to the above question is 10, what is the value of unknown variable x?

### Answer:
