We have numbers 7908 and 1001. Let's start adding them 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 0 & 0 in column 2 and get 0.

Step 3: We'll start by adding the digits 9 & 0 in column 3 and get 9.

Step 4: We'll start by adding the digits 7 & 1 in column 4 and get 8.

So, 7908 + 1001 = 8909.

