Answer:
is the constant of proportionality in terms of the cost per shirt .
Step-by-step explanation:
Constant of proportionality
Let us assume that x is proportional to y .

x = ky
Where k is the constant of proportionality .
As given
Josh takes a load of dress shirts to the dry cleaners.
The amount he pays for dry cleaning f is given by the equation 
where s is the number of shirts.
Compare
with x = ky .
Thus

Therefore
is the constant of proportionality in terms of the cost per shirt .