OK, let's do this. We've got 76139 and 17942, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 2 and the borrow 0 from 9 in column 1 and get 7.
7 is the first digit of our result.

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 3 in column 2 and get -1.
We add -1 to 10 and get 9 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 7 and the borrow 1 from 6 in column 4 and get -2.
We add -2 to 10 and get 8 as the next digit of the result.

Step 5: We'll start by subtracting the digit 1 and the borrow 1 from 7 in column 5 and get 5.
5 is the next digit of our result.

So, 76139 - 17942 = 58197.