Here \(\displaystyle{A}={\left\lbrace{x}\ {i}{s}\ {a}\ {n}{a}{t}{u}{r}{a}{l}\ nu{m}{b}{e}{r}{\quad\text{and}\quad}{f}{a}{c}to{r}\ {o}{f}\ {18}\right\rbrace}\).

\(={\left\lbrace{1},{2},{3},{6},{9},{18}\right\rbrace}{A}={\left\lbrace{x}\ {i}{s}\ {a}\ {n}{a}{t}{u}{r}{a}{l}\ nu{m}{b}{e}{r}{\quad\text{and}\quad}{f}{a}{c}to{r}\ {o}{f}\ {18}\right\rbrace}\)

\(={\left\lbrace{1},{2},{3},{6},{9},{18}\right\rbrace}{\quad\text{and}\quad}{B}={\left\lbrace{x}\ {i}{s}\ {a}\ {n}{a}{t}{u}{r}{a}{l}\ nu{m}{b}{e}{r}{\quad\text{and}\quad}\ le{s}{s}\ {t}{h}{a}{n}\ {6}\right\rbrace}\)

\(={\left\lbrace{1},{2},{3},{4},{5}\right\rbrace}.{B}={\left\lbrace{x}\ {i}{s}\ {a}\ {n}{a}{t}{u}{r}{a}{l}\ nu{m}{b}{e}{r}{\quad\text{and}\quad}\ le{s}{s}\ {t}{h}{a}{n}\ {6}\right\rbrace}={\left\lbrace{1},{2},{3},{4},{5}\right\rbrace}\)

Therefore,

\(A\cup B\ and A\cap B=\{1,2,3,4,5,6,9,18\}=\{1,2,3\}.\)

\(A\cup B = \{1,2,3,4,5,6,9,18\}\)

and

\(A\cap B = \{1,2,3\}. \)