We've got two numbers: 4221 and 1258. Let's find their sum.

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

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

Step 3: We'll start by adding the digits 2 & 2 in column 3 and get 4.

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

So, 4221 + 1258 = 5479.

