Not to worry, we've got 8520 and 149. Let's get to adding them!

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

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

Step 3: We'll start by adding the digits 5 & 1 in column 3 and get 6.

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

So, 8520 + 149 = 8669.

