Not to worry, we've got 4356 and 2505. Let's get to adding them!

Step 1: We'll start by adding the digits 6 & 5 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 5 & 0 in column 2 and get 6.

Step 3: We'll start by adding the digits 3 & 5 in column 3 and get 8.

Step 4: We'll start by adding the digits 4 & 2 in column 4 and get 6.

So, 4356 + 2505 = 6861.

