Is this a correct method for proving that $A - B\subseteq A$?

Question

I am not sure how to prove this because by definition, $A - B = \{x: x\in A | x\not\in B\}$.

So we know by definition that there is an element or elements of set $A$ in set $A - B$.

Maybe I could formally show this as: suppose $x\in(A - B)$, then $x\in A$. If $x\in A$, then $A - B\subseteq A$.