A container filled with 14 king melons has a mass of 6.99 kg. The same container when filled with 8 pomegranates has a mass of 1.23 kg. The mass of 1 king melon is four times the mass of 1 pomegranate. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

6.99 kg = 6990 g
1.23 kg = 1230 g

1 pomegranate = 1 u
8 pomegranates = 8 x 1 u = 8 u

1 container + 8 pomegranates = 1230
1 container + 8 u = 1230 --- (1)

1 king melon = 4 u
14 king melons = 14 x 4 u = 56 u

1 container + 14 king melons = 6990
1 container + 56 u = 6990 --- (2)

(2) - (1)
56 u - 8 u = 6990 - 1230
48 u = 5760

1 u = 5760 ÷ 48 = 120

8 u = 8 x 120 = 960

From (1):
1 container + 8 u = 1230
1 container + 960 = 1230
 
1 container = 1230 - 960 = 270

Mass of 1 container = 270 g

Answer(s): 270 g