We are presented with 421 and 9098. Let's work out the sum.

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 2 & 9 in column 2 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 4 & 0 in column 3 and get 5.

Step 4: We'll start by adding the digits 0 & 9 in column 4 and get 9.

So, 421 + 9098 = 9519.

