Okay, we are given 7925 and 3870. Let's add them up step by step.

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

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

Step 3: We'll start by adding the digits 9 & 8 in column 3 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 7 & 3 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 7925 + 3870 = 11795.

