We are presented with 2643 and 4056. Let's work out the sum.

Step 1: We'll start by adding the digits 3 & 6 in column 1 and get 9.

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 6 & 0 in column 3 and get 6.

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

So, 2643 + 4056 = 6699.

