Okay, we are given 20 and 370. Let's add them up step by step.

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

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

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

So, 20 + 370 = 390.

