We have numbers 3205 and 4315. Let's start adding them together.

Step 1: We'll start by adding the digits 5 & 5 in column 1 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 1 in column 2 and get 2.

Step 3: We'll start by adding the digits 2 & 3 in column 3 and get 5.

Step 4: We'll start by adding the digits 3 & 4 in column 4 and get 7.

So, 3205 + 4315 = 7520.

