A container filled with 12 jackfruits has a mass of 12.89 kg. The same container when filled with 8 mangoes has a mass of 1.49 kg. The mass of 1 jackfruit is seven times the mass of 1 mango. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

12.89 kg = 12890 g
1.49 kg = 1490 g

1 mango = 1 u
8 mangoes = 8 x 1 u = 8 u

1 container + 8 mangoes = 1490
1 container + 8 u = 1490 --- (1)

1 jackfruit = 7 u
12 jackfruits = 12 x 7 u = 84 u

1 container + 12 jackfruits = 12890
1 container + 84 u = 12890 --- (2)

(2) - (1)
84 u - 8 u = 12890 - 1490
76 u = 11400

1 u = 11400 ÷ 76 = 150

8 u = 8 x 150 = 1200

From (1):
1 container + 8 u = 1490
1 container + 1200 = 1490
 
1 container = 1490 - 1200 = 290

Mass of 1 container = 290 g

Answer(s): 290 g