A wooden crate half full of pineapples has a mass of 14kg. The same crate one third full of pineapples has a mass of 12 kg. What is the mass of the empty crate?

Please help, many thanks.

If an empty crate weighs x, and a full crate contains y kg of fruit, then

x + y/2 = 14
x + y/3 = 12

Now just find x.