Things could have been worded a little differently - seems understandable for you to be missing what you're missing.
Say $V$ is the original vector space and $H$ is our hyperplane. The definition means that there _exists_ a vector $x$ such that $H$ and $x$ generate $V$. The problem asks you to show that $H$ and $x$ generate $V$ for _every_ $x$ (in $V$ but not in $H$).
HINT: Say $V$ is generated by $H$ and $x_0$. Say $x$ is a vector in $V$ which is not in $H$. Now _since_ $H$ and $x_0$ generate $V$ it follows that $x=???$, and then the fact that $x$ is not in $H$ shows that ???