OK, let's do this. We've got 2015 and 4343 and we're adding them all together.

Step 1: We'll start by adding the digits 5 & 3 in column 1 and get 8.

Step 2: We'll start by adding the digits 1 & 4 in column 2 and get 5.

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

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

So, 2015 + 4343 = 6358.

