A container filled with 12 watermelons has a mass of 13.17 kg. The same container when filled with 8 mangosteens has a mass of 1.65 kg. The mass of 1 watermelon is six times the mass of 1 mangosteen. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

13.17 kg = 13170 g
1.65 kg = 1650 g

1 mangosteen = 1 u
8 mangosteens = 8 x 1 u = 8 u

1 container + 8 mangosteens = 1650
1 container + 8 u = 1650 --- (1)

1 watermelon = 6 u
12 watermelons = 12 x 6 u = 72 u

1 container + 12 watermelons = 13170
1 container + 72 u = 13170 --- (2)

(2) - (1)
72 u - 8 u = 13170 - 1650
64 u = 11520

1 u = 11520 ÷ 64 = 180

8 u = 8 x 180 = 1440

From (1):
1 container + 8 u = 1650
1 container + 1440 = 1650
 
1 container = 1650 - 1440 = 210

Mass of 1 container = 210 g

Answer(s): 210 g