Okay, we are tasked with adding 8690 and 1900. Let's begin!

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

Step 2: We'll start by adding the digits 9 & 0 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 8690 + 1900 = 10590.

