Okay, we are given 231 and 664. Let's add them up step by step.

Step 1: We'll start by adding the digits 1 & 4 in column 1 and get 5.

Step 2: We'll start by adding the digits 3 & 6 in column 2 and get 9.

Step 3: We'll start by adding the digits 2 & 6 in column 3 and get 8.

So, 231 + 664 = 895.

