We are presented with 3521 and 5238. Let's work out the sum.

Step 1: We'll start by adding the digits 1 & 8 in column 1 and get 9.

Step 2: We'll start by adding the digits 2 & 3 in column 2 and get 5.

Step 3: We'll start by adding the digits 5 & 2 in column 3 and get 7.

Step 4: We'll start by adding the digits 3 & 5 in column 4 and get 8.

So, 3521 + 5238 = 8759.

