We are presented with 9407 and 4381. Let's work out the sum.

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

Step 2: We'll start by adding the digits 0 & 8 in column 2 and get 8.

Step 3: We'll start by adding the digits 4 & 3 in column 3 and get 7.

Step 4: We'll start by adding the digits 9 & 4 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 9407 + 4381 = 13788.

