A television station shows 3 commercials every 12 minutes. At this rate, how many commercials will the station show in 84 minutes?

It will take 72 mins to see 18 commercials.
Step-by-step explanation:
If a television station shows commercials every 12 mins, then to figure out how long it takes to see 18 commercials you will have to do 18 / 3 which is 6. Then do 12 * 6 and you will get 72 mins.
Another method is finding the unit rate of how long does it take to see one commercial. So in order to do that, you will have to do 12 / 3, and you will get 4. So, to see one commercial it will take 4 mins. But you want to find how long will it take to see 18 commercials. So you do 18 * 4 which equals 72 mins.