The northbound bus arrives at the station every 15 minutes. The
southbound bus arrives at the
station every 20 minutes. If both
buses leave at the same time, how
long will it be before both buses
arrive back at the same time?

Acompany manufactures three types of cabinets. it makes 110 cabinets each week. in the first week, the sum of the number of type-1 cabinets and twice the number of type-2 cabinets produced was 10 more than the number of type-3 cabinets produced. the next week, the number of type-1 cabinets produced was three times more than in the first week, no type-2 cabinets were produced, and the number of type-3 cabinets produced was the same as in the previous week.