Not to worry, we've got 42 and 3951. Let's get to adding them!

Step 1: We'll start by adding the digits 2 & 1 in column 1 and get 3.

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 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 3 in column 4 and get 3.

So, 42 + 3951 = 3993.

