Answer:
The equation is c=2n
The constant of proportionality is 2
$18 will buy 9 cups of coffee
Step-by-step explanation:
Cost c=2*n
where c is the number of cups
The constant of proportion is 2
If cost is $18, then
18 = 2n
n = 18/2
n = 9
$18 will purchase 9 cups of coffee
