Image of Set Difference under Relation

Theorem
Let $$\mathcal{R} \subseteq S \times T$$ be a relation. Let $$A$$ and $$B$$ be subsets of $$S$$. Then:

$$\mathcal{R} \left({A}\right) - \mathcal{R} \left({B}\right) \subseteq \mathcal{R} \left({A - B}\right)$$