I've got this problem from my SAT Math level 2 prep book, which I think has the wrong answer.

The question is:

So what I did was subtract the matrix on the right by the left, and then both multiply both sides by -1.

The answer I get is

(-4 1 -11)

8 -1 -2

However in the book, the answer saysb)

I have never done matrices before reading this book, and I'm trying to learn from the book. This is proving difficult as this book is quite hard to read, although I correctly answered the previous questions.