When an ice box is packed with 15 identical bottles of soda, it has a mass of 14.2 kg. When the ice box is packed with 25 identical packets of milo, it has a mass of 9.05 kg. A bottle of soda weighs 510 g more than a packet of milo. What is the mass of the empty ice box in kg?
1000 g = 1 kg
510 g = 510 ÷ 1000 = 0.51 kg

Mass of 1 packet of milo = 1 P
Mass of 1 bottle of soda = 1 P + 0.51

Mass of 25 packets of milo = 25 P
Mass of 15 bottles of soda = 15(1 P + 0.51) = 15 P + 7.65 

Ice Box + 15 P = 14.2 - 7.65 = 6.55
Ice Box + 15 P = 6.55 --- (1)

Ice Box + 25 P = 9.05 --- (2)

(2) - (1)
25 P - 15 P = 9.05 - 6.55 
10 P = 2.5

1 P = 2.5 ÷ 10 = 0.25

15 P = 15 x 0.25 = 3.75

Mass of the empty ice box
= 6.55 - 3.75
= 2.8 kg

Answer(s): 2.8 kg