$r$, $a$, $b$ and $n$ are vectors; I need to find $r$ in terms of the others for
(1) $r\cdot n = 3$;
(2) $r + \alpha\cdot a = b$.
Could anyone please give me a hint on how to start? I thought about doing the dot product of the second equation with $n$, but it didn't help too much.
There may be no solution.