OK, let's do this. We've got 3500 and 6187 and we're adding them all together.

Step 1: We'll start by adding the digits 0 & 7 in column 1 and get 7.

Step 2: We'll start by adding the digits 0 & 8 in column 2 and get 8.

Step 3: We'll start by adding the digits 5 & 1 in column 3 and get 6.

Step 4: We'll start by adding the digits 3 & 6 in column 4 and get 9.

So, 3500 + 6187 = 9687.

