How am I supposed to solve question 8? I tried, but couldn`t get to the answer. I`ve attached an image, it`s question 8. Please help me out. Thanks

Thanks. As I said, I tried solving this question. And I did get to this point, when a, b & c came out to be 2, 4, and 2 respectively. But it doesn`t matches the answer at the back of the book. The answer is a/1 = b/2 = c/(-1)