A container filled with 11 king melons has a mass of 10.14 kg. The same container when filled with 7 lemons has a mass of 1.29 kg. The mass of 1 king melon is six times the mass of 1 lemon. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

10.14 kg = 10140 g
1.29 kg = 1290 g

1 lemon = 1 u
7 lemons = 7 x 1 u = 7 u

1 container + 7 lemons = 1290
1 container + 7 u = 1290 --- (1)

1 king melon = 6 u
11 king melons = 11 x 6 u = 66 u

1 container + 11 king melons = 10140
1 container + 66 u = 10140 --- (2)

(2) - (1)
66 u - 7 u = 10140 - 1290
59 u = 8850

1 u = 8850 ÷ 59 = 150

7 u = 7 x 150 = 1050

From (1):
1 container + 7 u = 1290
1 container + 1050 = 1290
 
1 container = 1290 - 1050 = 240

Mass of 1 container = 240 g

Answer(s): 240 g