We are presented with 9645 and 5843. Let's work out the sum.

Step 1: We'll start by adding the digits 5 & 3 in column 1 and get 8.

Step 2: We'll start by adding the digits 4 & 4 in column 2 and get 8.

Step 3: We'll start by adding the digits 6 & 8 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 9 & 5 in column 4 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 9645 + 5843 = 15488.

