For this case what we can do is the following rule of three: 2/3 of a box ------> 1/2 minutes x of a box ---------> 1 minute Clearing x we have: x = (1 / (1/2)) * (2/3) Rewriting: x = 2 * (2/3) x = 4/3 Answer: the number of boxes per minute that the machine packs is: x = 4/3