y varies inversely as x and y= 0.5 when x=24
What is your question or concern?
The only thing I can make out of this is that you want the function where y is an inverse of x and $\displaystyle f(24)=0.5$
Let $\displaystyle f(x)=\frac{a}{x}$
$\displaystyle 0.5 = \frac{a}{24}$
$\displaystyle a = 12$
Therefore, our function is $\displaystyle f(x) = \frac{12}{x}$