Okay, we are given 975 and 402. Let's add them up step by step.

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

Step 2: We'll start by adding the digits 7 & 0 in column 2 and get 7.

Step 3: We'll start by adding the digits 9 & 4 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 975 + 402 = 1377.

