Okay, we are given 1001 and 3790. Let's add them up step by step.

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

Step 2: We'll start by adding the digits 0 & 9 in column 2 and get 9.

Step 3: We'll start by adding the digits 0 & 7 in column 3 and get 7.

Step 4: We'll start by adding the digits 1 & 3 in column 4 and get 4.

So, 1001 + 3790 = 4791.

