The cost, c, of a ham sandwich at a deli varies directly with the number of sandwiches, n. If c = $54 when n is 9, what is the cost of the sandwiches when n is 3? ...

We can find the cost of sandwiches with this equation:

c = x*n, where x is the cost per sandwich and n is the number of sandwiches.

If c = $54 when n = 9, then we can find x.

c = x*n

54 = 9x

x = $6

The cost per sandwich is $6.

When n = 3, then c = x*n = ($6) (3) = $18

When n is 3, the cost of the sandwiches is $18.