Not to worry, we've got 3540 and 4055. Let's get to adding them!

Step 1: We'll start by adding the digits 0 & 5 in column 1 and get 5.

Step 2: We'll start by adding the digits 4 & 5 in column 2 and get 9.

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

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

So, 3540 + 4055 = 7595.

