When an ice box is packed with 20 identical bottles of soda, it has a mass of 15.1 kg. When the ice box is packed with 25 identical packets of green tea, it has a mass of 8.95 kg. A bottle of soda weighs 360 g more than a packet of green tea. What is the mass of the empty ice box in kg?
1000 g = 1 kg
360 g = 360 ÷ 1000 = 0.36 kg

Mass of 1 packet of green tea = 1 P
Mass of 1 bottle of soda = 1 P + 0.36

Mass of 25 packets of green tea = 25 P
Mass of 20 bottles of soda = 20(1 P + 0.36) = 20 P + 7.2 

Ice Box + 20 P = 15.1 - 7.2 = 7.9
Ice Box + 20 P = 7.9 --- (1)

Ice Box + 25 P = 8.95 --- (2)

(2) - (1)
25 P - 20 P = 8.95 - 7.9 
5 P = 1.05

1 P = 1.05 ÷ 5 = 0.21

20 P = 20 x 0.21 = 4.2

Mass of the empty ice box
= 7.9 - 4.2
= 3.7 kg

Answer(s): 3.7 kg