Let's get this math done. We have 3529 and 121 and we're going to add them all together.

Step 1: We'll start by adding the digits 9 & 1 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 2 & 2 in column 2 and get 5.

Step 3: We'll start by adding the digits 5 & 1 in column 3 and get 6.

Step 4: We'll start by adding the digits 3 & 0 in column 4 and get 3.

So, 3529 + 121 = 3650.

