When an ice box is packed with 15 identical bottles of soda, it has a mass of 10.4 kg. When the ice box is packed with 30 identical packets of coffee, it has a mass of 8.3 kg. A bottle of soda weighs 330 g more than a packet of coffee. What is the mass of the empty ice box in kg?
1000 g = 1 kg
330 g = 330 ÷ 1000 = 0.33 kg

Mass of 1 packet of coffee = 1 P
Mass of 1 bottle of soda = 1 P + 0.33

Mass of 30 packets of coffee = 30 P
Mass of 15 bottles of soda = 15(1 P + 0.33) = 15 P + 4.95 

Ice Box + 15 P = 10.4 - 4.95 = 5.45
Ice Box + 15 P = 5.45 --- (1)

Ice Box + 30 P = 8.3 --- (2)

(2) - (1)
30 P - 15 P = 8.3 - 5.45 
15 P = 2.85

1 P = 2.85 ÷ 15 = 0.19

15 P = 15 x 0.19 = 2.85

Mass of the empty ice box
= 5.45 - 2.85
= 2.6 kg

Answer(s): 2.6 kg