Answer:
[tex]qurtile1 = (\frac{n + 1}{4})th \: item \\ = (\frac{15 + 1}{4})th \: item \\ = 4th \: item \\ quartile1 = 10 \\ now \\ quartile2 =( \frac{n + 1}{2})th \: item \\ = ( \frac{15 + 1}{2})th \: item \\ = 8th \: item \\ quartile2 = 18 \\ again \\ quartile3 = 3( \frac{n + 1}{4})th \: item \\ = 3( \frac{15 + 1}{4})th \: item \\ = 12th \: item \\ quartile3 = 40[/tex]