The table shows the number of bracelets purchased and their cost. Find the missing value from the table if the number of bracelets and the cost are proportional.

Number of bracelets	$3$	$9$	$27$
Cost (in $\$$)	$2.5$	$7.5$	$?$

The correct option is B $\$22.5$
From the table, we can see:

Number of bracelets	Cost (in $\$$)	Cost per bracelet ($\$$ per unit)
$3$	$2.5$	$\frac{2.5}{3}=\frac{5}{6}$
$9$	$7.5$	$\frac{7.5}{9}=\frac{15}{18}=\frac{5}{6}$
$27$	$x$	$\frac{x}{27}$

Here, the constant of proportionality is $\frac{5}{6}$.
Since the number of bracelets are proportional to the cost, we have: $\frac{x}{27}=\frac{5}{6}$
$x=\frac{5}{6}\times 27=\frac{5}{2}\times 9=\frac{45}{2}=22.5$
Therefore, the missing value should be $\$22.5$.