Answer:
60 weeks
Step-by-step explanation:
Factor both numbers 12 and 15:
Find LCM(12,15). The common factor is only 3, multiply ths common factor by all factors that remain. Then
[tex]LCM(12,15)=3\cdot 2\cdot 2\cdot 5=60.[/tex]
This means that the fewest number of weeks that will pass before both machines are cleaned again in the same week is 60 weeks.