We've got two numbers: 31 and 1535. Let's find their sum.

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

Step 2: We'll start by adding the digits 3 & 3 in column 2 and get 6.

Step 3: We'll start by adding the digits 0 & 5 in column 3 and get 5.

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

So, 31 + 1535 = 1566.

