Answer:
6 hours.
Step-by-step explanation:
Let t represent the time taken by apprentice in hours to make a set of glasses when working alone.
Part of work completed by apprentice in one hour would be .
We have been given that a glassblower can produce a set of simple glasses in about 2 hours. So part of work completed by glassblower in one hour would be .
While working together, the job takes about 1.5 hours. So part of work completed by both in one hour would be .
Now we will equate sum of work competed by both in hour by work completed by both working together is one hour as:
Therefore, it will take 6 hours for the apprentice to make a set of glasses when working alone.