We are presented with 3557 and 4212. Let's work out the sum.

Step 1: We'll start by adding the digits 7 & 2 in column 1 and get 9.

Step 2: We'll start by adding the digits 5 & 1 in column 2 and get 6.

Step 3: We'll start by adding the digits 5 & 2 in column 3 and get 7.

Step 4: We'll start by adding the digits 3 & 4 in column 4 and get 7.

So, 3557 + 4212 = 7769.

