We've got two numbers: 9151 and 9712. Let's find their sum.

Step 1: We'll start by adding the digits 1 & 2 in column 1 and get 3.

Step 2: We'll start by adding the digits 5 & 1 in column 2 and get 6.

Step 3: We'll start by adding the digits 1 & 7 in column 3 and get 8.

Step 4: We'll start by adding the digits 9 & 9 in column 4 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

So, 9151 + 9712 = 18863.

