1. Problem (6): Calculate the mass of 30 bags each weighing 15 kg. To find the total mass, multiply the number of bags by the mass of one bag: $$\text{Total mass} = 30 \times 15$$ $$= 450\text{ kg}$$ 2. Problem (7): Calculate the total number of buttons on shirts. Each shirt has 5 buttons. There are 30 shirts on each shelf and 5 shelves. First find total shirts: $$30 \times 5 = 150$$ Then find total buttons: $$150 \times 5 = 750$$ buttons 3. Problem (8): Calculate total money collected from soft drinks and fruit drinks. Soft drinks sold: 40 at $1.25 each. Fruit drinks sold: 30 at $1.50 each. Calculate revenue: Soft drinks: $$40 \times 1.25 = 50$$ Fruit drinks: $$30 \times 1.50 = 45$$ Total money collected: $$50 + 45 = 95$$ 4. Problem (9): Calculate number of bottles on 5 filled trays. One carton holds 24 bottles. 12 cartons fill one tray. So bottles per tray: $$24 \times 12 = 288$$ For 5 trays: $$288 \times 5 = 1440$$ bottles Final answers: (6) 450 kg (7) 750 buttons (8) 95 total money collected (9) 1440 bottles