A container filled with 9 mangoes has a mass of 13.87 kg. The same container when filled with 9 starfruits has a mass of 1.9 kg. The mass of 1 mango is eight times the mass of 1 starfruit. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

13.87 kg = 13870 g
1.9 kg = 1900 g

1 starfruit = 1 u
9 starfruits = 9 x 1 u = 9 u

1 container + 9 starfruits = 1900
1 container + 9 u = 1900 --- (1)

1 mango = 8 u
9 mangoes = 9 x 8 u = 72 u

1 container + 9 mangoes = 13870
1 container + 72 u = 13870 --- (2)

(2) - (1)
72 u - 9 u = 13870 - 1900
63 u = 11970

1 u = 11970 ÷ 63 = 190

9 u = 9 x 190 = 1710

From (1):
1 container + 9 u = 1900
1 container + 1710 = 1900
 
1 container = 1900 - 1710 = 190

Mass of 1 container = 190 g

Answer(s): 190 g