We've got two numbers: 6404 and 2572. Let's find their sum.

Step 1: We'll start by adding the digits 4 & 2 in column 1 and get 6.

Step 2: We'll start by adding the digits 0 & 7 in column 2 and get 7.

Step 3: We'll start by adding the digits 4 & 5 in column 3 and get 9.

Step 4: We'll start by adding the digits 6 & 2 in column 4 and get 8.

So, 6404 + 2572 = 8976.

