OK, let's do this. We've got 5018 and 1381 and we're adding them all together.

Step 1: We'll start by adding the digits 8 & 1 in column 1 and get 9.

Step 2: We'll start by adding the digits 1 & 8 in column 2 and get 9.

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 5 & 1 in column 4 and get 6.

So, 5018 + 1381 = 6399.

