Okay, we are given 8464 and 423. Let's add them up step by step.

Step 1: We'll start by adding the digits 4 & 3 in column 1 and get 7.

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

Step 3: We'll start by adding the digits 4 & 4 in column 3 and get 8.

Step 4: We'll start by adding the digits 8 & 0 in column 4 and get 8.

So, 8464 + 423 = 8887.

