Alright, let's solve this problem step by step. We have 1040 and 6521 and we're adding them together.

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

Step 2: We'll start by adding the digits 4 & 2 in column 2 and get 6.

Step 3: We'll start by adding the digits 0 & 5 in column 3 and get 5.

Step 4: We'll start by adding the digits 1 & 6 in column 4 and get 7.

So, 1040 + 6521 = 7561.

