When an ice box is packed with 25 identical bottles of coke, it has a mass of 20.7 kg. When the ice box is packed with 35 identical packets of orange juice, it has a mass of 13.35 kg. A bottle of coke weighs 410 g more than a packet of orange juice. What is the mass of the empty ice box in kg?
1000 g = 1 kg
410 g = 410 ÷ 1000 = 0.41 kg

Mass of 1 packet of orange juice = 1 P
Mass of 1 bottle of coke = 1 P + 0.41

Mass of 35 packets of orange juice = 35 P
Mass of 25 bottles of coke = 25(1 P + 0.41) = 25 P + 10.25 

Ice Box + 25 P = 20.7 - 10.25 = 10.45
Ice Box + 25 P = 10.45 --- (1)

Ice Box + 35 P = 13.35 --- (2)

(2) - (1)
35 P - 25 P = 13.35 - 10.45 
10 P = 2.9

1 P = 2.9 ÷ 10 = 0.29

25 P = 25 x 0.29 = 7.25

Mass of the empty ice box
= 10.45 - 7.25
= 3.2 kg

Answer(s): 3.2 kg