Sure thing! We've got 172429 and 70420, and we're going to subtract the second number from the first.

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

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

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

Step 4: We'll start by subtracting the digit 0 and the borrow 0 from 2 in column 4 and get 2.
2 is the next digit of our result.

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

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 1 in column 6 and get 1.
1 is the next digit of our result.

So, 172429 - 70420 = 102009.