Let's dive into this subtraction. We'll start with 75124 and subtract 34958 from it.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 4 in column 1 and get -4.
We add -4 to 10 and get 6 as the first digit of the result.

Step 2: We'll start by subtracting the digit 5 and the borrow 1 from 2 in column 2 and get -4.
We add -4 to 10 and get 6 as the next digit of the result.

Step 3: We'll start by subtracting the digit 9 and the borrow 1 from 1 in column 3 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 4: We'll start by subtracting the digit 4 and the borrow 1 from 5 in column 4 and get 0.
0 is the next digit of our result.

Step 5: We'll start by subtracting the digit 3 and the borrow 0 from 7 in column 5 and get 4.
4 is the next digit of our result.

So, 75124 - 34958 = 40166.