Let's solve this addition problem. We have 4087 and 128, and we need to add them together.

Step 1: We'll start by adding the digits 7 & 8 in column 1 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 8 & 2 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 0 & 1 in column 3 and get 2.

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

So, 4087 + 128 = 4215.

