When an ice box is packed with 25 identical bottles of coke, it has a mass of 14.65 kg. When the ice box is packed with 35 identical packets of orange juice, it has a mass of 7.1 kg. A bottle of coke weighs 350 g more than a packet of orange juice. What is the mass of the empty ice box in kg?
1000 g = 1 kg
350 g = 350 ÷ 1000 = 0.35 kg

Mass of 1 packet of orange juice = 1 P
Mass of 1 bottle of coke = 1 P + 0.35

Mass of 35 packets of orange juice = 35 P
Mass of 25 bottles of coke = 25(1 P + 0.35) = 25 P + 8.75 

Ice Box + 25 P = 14.65 - 8.75 = 5.9
Ice Box + 25 P = 5.9 --- (1)

Ice Box + 35 P = 7.1 --- (2)

(2) - (1)
35 P - 25 P = 7.1 - 5.9 
10 P = 1.2

1 P = 1.2 ÷ 10 = 0.12

25 P = 25 x 0.12 = 3

Mass of the empty ice box
= 5.9 - 3
= 2.9 kg

Answer(s): 2.9 kg