Alright, let's solve this problem step by step. We have 2905 and 1620 and we're adding them together.

Step 1: We'll start by adding the digits 5 & 0 in column 1 and get 5.

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

Step 3: We'll start by adding the digits 9 & 6 in column 3 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 2 & 1 in column 4 and get 4.

So, 2905 + 1620 = 4525.

