Okay, we are tasked with adding 1123 and 7258. Let's begin!

Step 1: We'll start by adding the digits 3 & 8 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 2 & 5 in column 2 and get 8.

Step 3: We'll start by adding the digits 1 & 2 in column 3 and get 3.

Step 4: We'll start by adding the digits 1 & 7 in column 4 and get 8.

So, 1123 + 7258 = 8381.

