When an ice box is packed with 10 identical bottles of soda, it has a mass of 7.1 kg. When the ice box is packed with 15 identical packets of coffee, it has a mass of 4.2 kg. A bottle of soda weighs 370 g more than a packet of coffee. What is the mass of the empty ice box in kg?
1000 g = 1 kg
370 g = 370 ÷ 1000 = 0.37 kg

Mass of 1 packet of coffee = 1 P
Mass of 1 bottle of soda = 1 P + 0.37

Mass of 15 packets of coffee = 15 P
Mass of 10 bottles of soda = 10(1 P + 0.37) = 10 P + 3.7 

Ice Box + 10 P = 7.1 - 3.7 = 3.4
Ice Box + 10 P = 3.4 --- (1)

Ice Box + 15 P = 4.2 --- (2)

(2) - (1)
15 P - 10 P = 4.2 - 3.4 
5 P = 0.8

1 P = 0.8 ÷ 5 = 0.16

10 P = 10 x 0.16 = 1.6

Mass of the empty ice box
= 3.4 - 1.6
= 1.8 kg

Answer(s): 1.8 kg