Solution:
As, we have to find , [tex]3 \frac{1}{2} of 20=\frac{7}{2}[/tex]% of 20
[tex]= \frac{7}{2\times 100}\times 20\\\\ = \frac{7}{10} \\\\ =0.70[/tex]
If we have to Percent of a certain number it means , divide that number by 100 , for example x% means [tex]\frac{x}{100}[/tex].
And if i am writing , x% of y it means , [tex]\frac{xy}{100}[/tex].