A container filled with 9 durians has a mass of 12.13 kg. The same container when filled with 3 lemons has a mass of 0.73 kg. The mass of 1 durian is seven 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

12.13 kg = 12130 g
0.73 kg = 730 g

1 lemon = 1 u
3 lemons = 3 x 1 u = 3 u

1 container + 3 lemons = 730
1 container + 3 u = 730 --- (1)

1 durian = 7 u
9 durians = 9 x 7 u = 63 u

1 container + 9 durians = 12130
1 container + 63 u = 12130 --- (2)

(2) - (1)
63 u - 3 u = 12130 - 730
60 u = 11400

1 u = 11400 ÷ 60 = 190

3 u = 3 x 190 = 570

From (1):
1 container + 3 u = 730
1 container + 570 = 730
 
1 container = 730 - 570 = 160

Mass of 1 container = 160 g

Answer(s): 160 g