Let's solve this addition problem. We have 1211 and 126, and we need to add them together.

Step 1: We'll start by adding the digits 1 & 6 in column 1 and get 7.

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

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

Step 4: We'll start by adding the digits 1 & 0 in column 4 and get 1.

So, 1211 + 126 = 1337.

