We've got two numbers: 5164 and 1591. Let's find their sum.

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

Step 2: We'll start by adding the digits 6 & 9 in column 2 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 1 & 5 in column 3 and get 7.

Step 4: We'll start by adding the digits 5 & 1 in column 4 and get 6.

So, 5164 + 1591 = 6755.

