When an ice box is packed with 10 identical bottles of coke, it has a mass of 8.5 kg. When the ice box is packed with 20 identical packets of orange juice, it has a mass of 4.9 kg. A bottle of coke weighs 520 g more than a packet of orange juice. What is the mass of the empty ice box in kg?
1000 g = 1 kg
520 g = 520 ÷ 1000 = 0.52 kg

Mass of 1 packet of orange juice = 1 P
Mass of 1 bottle of coke = 1 P + 0.52

Mass of 20 packets of orange juice = 20 P
Mass of 10 bottles of coke = 10(1 P + 0.52) = 10 P + 5.2 

Ice Box + 10 P = 8.5 - 5.2 = 3.3
Ice Box + 10 P = 3.3 --- (1)

Ice Box + 20 P = 4.9 --- (2)

(2) - (1)
20 P - 10 P = 4.9 - 3.3 
10 P = 1.6

1 P = 1.6 ÷ 10 = 0.16

10 P = 10 x 0.16 = 1.6

Mass of the empty ice box
= 3.3 - 1.6
= 1.7 kg

Answer(s): 1.7 kg