We've got two numbers: 7887 and 4070. Let's find their sum.

Step 1: We'll start by adding the digits 7 & 0 in column 1 and get 7.

Step 2: We'll start by adding the digits 8 & 7 in column 2 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 8 & 0 in column 3 and get 9.

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

So, 7887 + 4070 = 11957.

