We've got two numbers: 4200 and 3545. Let's find their sum.

Step 1: We'll start by adding the digits 0 & 5 in column 1 and get 5.

Step 2: We'll start by adding the digits 0 & 4 in column 2 and get 4.

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

Step 4: We'll start by adding the digits 4 & 3 in column 4 and get 7.

So, 4200 + 3545 = 7745.

