A box filled with 8 honeydews has a mass of 4.1 kg. The same box when filled with 7 passion fruits has a mass of 1.1 kg. The mass of 1 honeydew is four times the mass of 1 passion fruit. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

4.1 kg = 4100 g
1.1 kg = 1100 g

1 passion fruit = 1 u
7 passion fruits = 7 x 1 u = 7 u

1 box + 7 passion fruits = 1100
1 box + 7 u = 1100 --- (1)

1 honeydew = 4 u
8 honeydews = 8 x 4 u = 32 u

1 box + 8 honeydews = 4100
1 box + 32 u = 4100 --- (2)

(2) - (1)
32 u - 7 u = 4100 - 1100
25 u = 3000

1 u = 3000 ÷ 25 = 120

7 u = 7 x 120 = 840

From (1):
1 box + 7 u = 1100
1 box + 840 = 1100
 
1 box = 1100 - 840 = 260

Mass of 1 box = 260 g

Answer(s): 260 g