If 12 eggs cost $2.04, you need to figure out how much 1 egg cost. In order to do that, you need to divide the cost ($2.04) by the amount of eggs (12):

1 egg = 0.17
Now that we know how much 1 egg costs, we need to take that number and multiply it by 18:

In this case, 18 eggs will cost
$3.06.