No, you can't cancel the dot product.

It's sometimes hard to keep track of which variables are "known" and which are "unknown". Here you are trying to express some vector x (which is therefore "known") as a combination of , , and , where a, b, and c are "known". The other variables - , , and are the coefficients we're looking for - they are "unknown".

So all you have to do is divide to get your answer:

-Hollywood