Let's get this math done. We have 8457 and 1517 and we're going to add them all together.

Step 1: We'll start by adding the digits 7 & 7 in column 1 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 5 & 1 in column 2 and get 7.

Step 3: We'll start by adding the digits 4 & 5 in column 3 and get 9.

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 9.

So, 8457 + 1517 = 9974.

