We can solve this together! We're beginning with 4345 and removing 2090 from it.

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

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 4 in column 2 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 3: We'll start by subtracting the digit 0 and the borrow 1 from 3 in column 3 and get 2.
2 is the next digit of our result.

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

So, 4345 - 2090 = 2255.