Let's solve this addition problem. We have 2091 and 4188, and we need to add them together.

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 9 & 8 in column 2 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 0 & 1 in column 3 and get 2.

Step 4: We'll start by adding the digits 2 & 4 in column 4 and get 6.

So, 2091 + 4188 = 6279.

