Okay, we are tasked with adding 7860 and 1400. Let's begin!

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

Step 2: We'll start by adding the digits 6 & 0 in column 2 and get 6.

Step 3: We'll start by adding the digits 8 & 4 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 7 & 1 in column 4 and get 9.

So, 7860 + 1400 = 9260.

