Anna started with 37 stamps in her collection.
Alison gave her half of her collection, which means Anna received 28/2 = 14 stamps from Alison.
After receiving the stamps from Alison, Anna had 37 + 14 = 51 stamps.
Then Anna traded Jeff x bluebird stamps for one mountain stamp.
After the trade, Anna had 51 - x bluebird stamps and 1 mountain stamp.
We are given that Anna had 50 stamps in the end, so we can write: 51 - x + 1 = 50.
Simplifying the left side, we get: 52 - x = 50.
Subtracting 52 from both sides, we get: -x = -2.
Multiplying both sides by -1, 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:
Anna, Alison, and Jeff collect stamps. Anna had 37 stamps in her collection, Alison had 28 stamps in her collection, and Jeff had 31 stamps in his collection. Alison gave Anna half of her collection in exchange for a novel, and then Anna traded Jeff x bluebird stamps for one mountain stamp. How many stamps did Anna have in the end?
If we know the answer to the above question is 50, what is the value of unknown variable x?

### Answer:
