We have numbers 6071 and 7128. Let's start adding them together.

Step 1: We'll start by adding the digits 1 & 8 in column 1 and get 9.

Step 2: We'll start by adding the digits 7 & 2 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 6 & 7 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 6071 + 7128 = 13199.

