Ready to do some math? We're starting with 4004 and 21 and adding them up.

Step 1: We'll start by adding the digits 4 & 1 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 0 & 0 in column 3 and get 0.

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

So, 4004 + 21 = 4025.

