We are presented with 6711 and 1725. Let's work out the 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 1 & 2 in column 2 and get 3.

Step 3: We'll start by adding the digits 7 & 7 in column 3 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 6 & 1 in column 4 and get 8.

So, 6711 + 1725 = 8436.

