Please be sure to `validate' your submissions, to make sure they really went through. The images shown in the validation view are exactly the same as those shown to the grading team.
Replacement Lemma : Let $V$ be a vector space, and $S$ a subset generating $V$, i.e. $\operatorname{span}(S)=V$. Suppose $v_1,\ldots,v_m\in V$ are linearly independent vectors. Then there exist distinct vectors $u_1,\ldots,u_m\in S$ such that the subset $$ (S\backslash \{u_1,\ldots,u_m\})\cup \{v_1,\ldots,v_m\}$$ spans V.