Answer 1

\[\text{ Let } z \in C - B . . . (1)\]
\[ \Rightarrow z \in C \text{ and } z \not\in B\]
\[ \Rightarrow z \in C \text{ and } z \not\in A \left[ \because A \subset B \right]\]
\[ \Rightarrow z \in C - A . . . (2)\]
\[\text{ From } (1) \text{ and } (2), \text{ we get }\]
\[C - B \subset C - A\]