A box filled with 8 honeydews has a mass of 9.88 kg. The same box when filled with 8 apples has a mass of 1.48 kg. The mass of 1 honeydew is eight times the mass of 1 apple. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

9.88 kg = 9880 g
1.48 kg = 1480 g

1 apple = 1 u
8 apples = 8 x 1 u = 8 u

1 box + 8 apples = 1480
1 box + 8 u = 1480 --- (1)

1 honeydew = 8 u
8 honeydews = 8 x 8 u = 64 u

1 box + 8 honeydews = 9880
1 box + 64 u = 9880 --- (2)

(2) - (1)
64 u - 8 u = 9880 - 1480
56 u = 8400

1 u = 8400 ÷ 56 = 150

8 u = 8 x 150 = 1200

From (1):
1 box + 8 u = 1480
1 box + 1200 = 1480
 
1 box = 1480 - 1200 = 280

Mass of 1 box = 280 g

Answer(s): 280 g