A container filled with 15 king melons has a mass of 12.84 kg. The same container when filled with 10 passion fruits has a mass of 1.64 kg. The mass of 1 king melon is six times the mass of 1 passion fruit. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

12.84 kg = 12840 g
1.64 kg = 1640 g

1 passion fruit = 1 u
10 passion fruits = 10 x 1 u = 10 u

1 container + 10 passion fruits = 1640
1 container + 10 u = 1640 --- (1)

1 king melon = 6 u
15 king melons = 15 x 6 u = 90 u

1 container + 15 king melons = 12840
1 container + 90 u = 12840 --- (2)

(2) - (1)
90 u - 10 u = 12840 - 1640
80 u = 11200

1 u = 11200 ÷ 80 = 140

10 u = 10 x 140 = 1400

From (1):
1 container + 10 u = 1640
1 container + 1400 = 1640
 
1 container = 1640 - 1400 = 240

Mass of 1 container = 240 g

Answer(s): 240 g