We have numbers 1245 and 8523. Let's start adding them together.

Step 1: We'll start by adding the digits 5 & 3 in column 1 and get 8.

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

Step 3: We'll start by adding the digits 2 & 5 in column 3 and get 7.

Step 4: We'll start by adding the digits 1 & 8 in column 4 and get 9.

So, 1245 + 8523 = 9768.

