Place Value Practice: Finding Numbers with Even Tens of Thousands Digits Below 43,125

To solve this problem, let's apply the following steps:

• Step 1: Verify that each choice is less than 43,125.
• Step 2: Determine the tens of thousands digit of each number.
• Step 3: Check which of these digits is even.

Now, let's apply these steps to the choices:

Step 1: Checking the choices against 43,125:

• $26,999$ is less than 43,125.
• $32,100$ is also less than 43,125.
• $44,123$ is greater than 43,125, so it's not suitable.
• $12,450$ is less than 43,125.

Step 2: Determine the tens of thousands digit for each remaining valid number:

• The tens of thousands digit of $26,999$ is 2.
• The tens of thousands digit of $32,100$ is 3.
• The tens of thousands digit of $12,450$ is 1.

Step 3: Check which tens of thousands digits are even:

• The digit 2 is even.
• The digits 3 and 1 are not even.

Therefore, out of the valid choices, the number $26,999$ has an even tens of thousands digit.

Thus, the correct choice, less than 43,125 with an even tens of thousands digit, is $26,999$.