Alright, let's solve this problem step by step. We have 1661 and 4121 and we're adding them together.

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

Step 2: We'll start by adding the digits 6 & 2 in column 2 and get 8.

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 7.

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

So, 1661 + 4121 = 5782.

