In these kind of problems, it is best to set up ratios and you have to be careful with your units.
Price of ground coffee beans:
Ratio of ounces to cups:
Now I need to find the cost of the ground coffee beans required to make 1 cup of brewed coffee. So, what we do first, is convert 1 cup into oz using the ratio given:
Notice that the cup unit cancel (and don't leave the s behind! ):
Now, last thing to do is to multiply the converted unit with the price:
Again, the units cancel, leaving you with the price: