When an ice box is packed with 15 identical bottles of soda, it has a mass of 13.3 kg. When the ice box is packed with 30 identical packets of green tea, it has a mass of 10 kg. A bottle of soda weighs 450 g more than a packet of green tea. What is the mass of the empty ice box in kg?
1000 g = 1 kg
450 g = 450 ÷ 1000 = 0.45 kg

Mass of 1 packet of green tea = 1 P
Mass of 1 bottle of soda = 1 P + 0.45

Mass of 30 packets of green tea = 30 P
Mass of 15 bottles of soda = 15(1 P + 0.45) = 15 P + 6.75 

Ice Box + 15 P = 13.3 - 6.75 = 6.55
Ice Box + 15 P = 6.55 --- (1)

Ice Box + 30 P = 10 --- (2)

(2) - (1)
30 P - 15 P = 10 - 6.55 
15 P = 3.45

1 P = 3.45 ÷ 15 = 0.23

15 P = 15 x 0.23 = 3.45

Mass of the empty ice box
= 6.55 - 3.45
= 3.1 kg

Answer(s): 3.1 kg