Let's solve the problem step-by-step:
1. We start with the initial amount: 20,000.
2. We need to subtract 10,000 from the initial amount.
3. Perform the subtraction:
[tex]\[
20,000 - 10,000 = 10,000
\][/tex]
So, the result is 10,000.
Therefore, the correct option is:
Diez mil