Lets define the variables:
[tex]X\colon\text{ students who play a sport}[/tex][tex]F\colon\text{ students who play football}[/tex][tex]H\colon\text{ total students of the high school}[/tex]we have that
[tex]X=\frac{2}{5}H\text{ }[/tex]and
[tex]F=\frac{1}{4}X\Rightarrow X=4F[/tex]then replacion X=4F, we have that
[tex]4F=\frac{2}{5}H\Rightarrow F=\frac{2}{5(4)}H\Rightarrow F=\frac{2}{20}H=\frac{1}{10}H[/tex]then 1/10 of students at west high school play football
