Alright, let's solve this problem step by step. We have 4394 and 4290 and we're adding them together.

Step 1: We'll start by adding the digits 4 & 0 in column 1 and get 4.

Step 2: We'll start by adding the digits 9 & 9 in column 2 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 3 & 2 in column 3 and get 6.

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

So, 4394 + 4290 = 8684.

