The dual space of a vector space $V$ is the vector space of all linear functionals on $V$. Denote the dual space of $V$ by $V'$.
Question: If $W$ is a subspace of a finite dimensional vector space $V$ and $f\in W'$, then there exists $g\in V'$ such that $f=g$ on $W$.
Any help on this please, I have no idea how to start. Thanks.