Let $\vec a=\hat i+2\hat j+\hat k$, $\quad \vec b=3(\hat i-\hat j+\hat k)$. Let $\vec c$ be the vector such that $\vec a\times\vec c=\vec b$ and $\vec a\cdot\vec c=3$. Then $\vec a\cdot\big((\vec c\times\vec b)-\vec b-\vec c\big)$ is equal to: