18 is what percent of 72

Divide 18 by 72:

$${\frac{{\mathtt{18}}}{{\mathtt{72}}}} = {\frac{{\mathtt{1}}}{{\mathtt{4}}}} = {\mathtt{0.25}}$$

0.25 is the same as 25%

$$\begin{array}{lcl} \dfrac{18}{72}&\times&\dfrac{100}{100}\\ \\ =\dfrac{18}{72}&\times&100*\dfrac{1}{100}\\\\ =\dfrac{18}{72}&\times&100*\%\\\\ =\dfrac{1800}{72}&\times& \% \\ \\ =\dfrac{1800}{72}\%\\\\ =25\% \end{array}\\$$