One person can do a certain job in twenty-one minutes, and another person can do the same job in twenty-eight minutes. How many minutes will it take them to do the job together? 6 min 12 min 24 min
if there are 2 people then doing the same job then that means divide by two so 8 which is off the 28 , 8 divided by 2 is 4, then, that makes 24 , and 24 divided by 2 is 12 so the answer is 12