A box filled with 11 mangoes has a mass of 9.95 kg. The same box when filled with 3 starfruits has a mass of 0.6 kg. The mass of 1 mango is eight times the mass of 1 starfruit. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

9.95 kg = 9950 g
0.6 kg = 600 g

1 starfruit = 1 u
3 starfruits = 3 x 1 u = 3 u

1 box + 3 starfruits = 600
1 box + 3 u = 600 --- (1)

1 mango = 8 u
11 mangoes = 11 x 8 u = 88 u

1 box + 11 mangoes = 9950
1 box + 88 u = 9950 --- (2)

(2) - (1)
88 u - 3 u = 9950 - 600
85 u = 9350

1 u = 9350 ÷ 85 = 110

3 u = 3 x 110 = 330

From (1):
1 box + 3 u = 600
1 box + 330 = 600
 
1 box = 600 - 330 = 270

Mass of 1 box = 270 g

Answer(s): 270 g