We've got two numbers: 70 and 3915. 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 7 & 1 in column 2 and get 8.

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 3 in column 4 and get 3.

So, 70 + 3915 = 3985.

