Answer :

To simplify 18/42, you would divide both numbers by 6.

18/6=3
42/6=7

That is in simplest form because you cannot simplify it anymore. Togather, that number is 3/7.

Hope this helped!
[tex] \frac{18}{42}= \frac{18\div2}{42\div2}=\frac{9}{21}=\frac{9\div3}{21\div3}=\boxed { \frac{3}{7} }[/tex]