Vector space/Generating system and spanning subspace/Fact

Let ${}K$ be a field and let ${}V$ be a ${}K$-vector space. Then the following hold.

1. Let ${}U_{j}$, ${}j\in J$, be a family of subspaces of ${}V$. Then the intersection

   ${}U=\bigcap _{j\in J}U_{j}\,$

   is a linear subspace.

2. Let ${}v_{i}$, ${}i\in I$, be a family of elements of ${}V$ and consider the subset ${}W$ of ${}V$ which is given by all linear combinations of these elements. Then ${}W$ is a linear subspace of ${}V$.
3. The family ${}v_{i}$, ${}i\in I$, is a system of generators of ${}V$ if and only if

   ${}\langle v_{i},\,i\in I\rangle =V\,.$

Write a proof