- $ \\\mathbb{N} \\\cap \\\mathbb{Z} = \\\mathbb{N}$.
- $ \\\mathbb{Q} \\\cup \\\mathbb{R} = \\\mathbb{R}$.
- $ \\\mathbb{Q} \\\cup {\\\mathbb{N}^*} = {\\\mathbb{N}^*}$.
- $ \\\mathbb{Q} \\\cap {\\\mathbb{N}^*} = {\\\mathbb{N}^*}$.