OK, let's do this. We've got 42890 and 42437, and we're subtracting the second number from the first.

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

Step 2: We'll start by subtracting the digit 3 and the borrow 1 from 9 in column 2 and get 5.
5 is the next digit of our result.

Step 3: We'll start by subtracting the digit 4 and the borrow 0 from 8 in column 3 and get 4.
4 is the next digit of our result.

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

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

So, 42890 - 42437 = 453.