Question 999285
Hi there,
coffee varies directly with the number of cans. 
C = kc (C = Coffee: c = cans)
Using the values to establish 'k'
the constant of proportionality.
C = kc
$18.50 = k2
k = $18.50/2
k = $9.25
Equation 
C = $9.25c
Hope this helps:-)