When an ice box is packed with 15 identical bottles of coke, it has a mass of 14 kg. When the ice box is packed with 20 identical packets of lemonade, it has a mass of 6.9 kg. A bottle of coke weighs 560 g more than a packet of lemonade. What is the mass of the empty ice box in kg?
1000 g = 1 kg
560 g = 560 ÷ 1000 = 0.56 kg

Mass of 1 packet of lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.56

Mass of 20 packets of lemonade = 20 P
Mass of 15 bottles of coke = 15(1 P + 0.56) = 15 P + 8.4 

Ice Box + 15 P = 14 - 8.4 = 5.6
Ice Box + 15 P = 5.6 --- (1)

Ice Box + 20 P = 6.9 --- (2)

(2) - (1)
20 P - 15 P = 6.9 - 5.6 
5 P = 1.3

1 P = 1.3 ÷ 5 = 0.26

15 P = 15 x 0.26 = 3.9

Mass of the empty ice box
= 5.6 - 3.9
= 1.7 kg

Answer(s): 1.7 kg