Let's solve this addition problem. We have 1428 and 7171, and we need to add them together.

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

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

Step 3: We'll start by adding the digits 4 & 1 in column 3 and get 5.

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

So, 1428 + 7171 = 8599.

