Work Step by Step
First, add the digits in the ones place. Since $9+6=15$, you have to "carry the one" to the tens place, and fill the ones place with the remainder, which is 5. When you add the digits in the tens place, you have to remember to also add the one that was carried over. $8+6+1=15$, so the final answer is 155. This matches the answer that was given in the book.