When an ice box is packed with 20 identical bottles of coke, it has a mass of 14.3 kg. When the ice box is packed with 35 identical packets of lemonade, it has a mass of 8.95 kg. A bottle of coke weighs 380 g more than a packet of lemonade. What is the mass of the empty ice box in kg?
1000 g = 1 kg
380 g = 380 ÷ 1000 = 0.38 kg

Mass of 1 packet of lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.38

Mass of 35 packets of lemonade = 35 P
Mass of 20 bottles of coke = 20(1 P + 0.38) = 20 P + 7.6 

Ice Box + 20 P = 14.3 - 7.6 = 6.7
Ice Box + 20 P = 6.7 --- (1)

Ice Box + 35 P = 8.95 --- (2)

(2) - (1)
35 P - 20 P = 8.95 - 6.7 
15 P = 2.25

1 P = 2.25 ÷ 15 = 0.15

20 P = 20 x 0.15 = 3

Mass of the empty ice box
= 6.7 - 3
= 3.7 kg

Answer(s): 3.7 kg