Hank started with a stock of bicycles.
On Friday, he sold 10 bicycles and bought 15, so the net change in the number of bicycles on Friday is 15 - 10 = 5.
On Saturday, he sold x bicycles and bought 8, so the net change in the number of bicycles on Saturday is 8 - x.
On Sunday, he sold 9 bicycles and bought 11, so the net change in the number of bicycles on Sunday is 11 - 9 = 2.
The net increase in the number of bicycles over the three days is the sum of the net changes on each day: 5 + (8 - x) + 2 = 15 - x.
We are given that the net increase in the number of bicycles is 3, so we can write: 15 - x = 3.
Solving for x, we get: x = 12.
The value of x is 12.
#### 12
The answer is: 12
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
On Friday, Hank opened his used-bicycle store with a stock of bicycles, all fixed-up and ready to ride. Over the course of the day, he sold 10 bicycles and bought an additional 15 to fix up. On Saturday, he sold x bicycles and bought 8 more. And on Sunday, he sold 9 bicycles and bought 11 more. What was the net increase in the number of bicycles in stock in Hank's store over the three days?
If we know the answer to the above question is 3, what is the value of unknown variable x?

### Answer:
