OK, let's do this. We've got 9122 and 390 and we're adding them all together.

Step 1: We'll start by adding the digits 2 & 0 in column 1 and get 2.

Step 2: We'll start by adding the digits 2 & 9 in column 2 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 1 & 3 in column 3 and get 5.

Step 4: We'll start by adding the digits 9 & 0 in column 4 and get 9.

So, 9122 + 390 = 9512.

