Three workers sort 66 boxes in a day. One of the workers is three times more productive than the second worker and twice as productive as the third worker. How many boxes did the second most productive worker sort?

Look at it this way ...there are 11 parts to the job

The first worker performs 6/11 of the job

The second worker performs 2/11 of the job

And the last worker performs 3/11 of the job

Then the second most productive worker sorts 66(3/11) = 18 boxes