18 workers
Answer:
4 workers can assemble 12 computers in 9 hours.
Since the number of hours is directly proportional to the number of computers:
4⋅12=48 computers could be assembled by 4 workers in 4⋅9=36 hours.
Since the number of hours is inversely proportional to the number of workers:
48 computers could be assembled by 92⋅4=18 workers in 29⋅36=8 hours.