If there are 3 cats but they each die of different diseases one of heart fail, second of Brian tumor and 3rd of experiment gone wrong, which how many cats are left.

none

Explanation:

It is given that there are 3 cats.

Each of the cats die with different diseases. One of cats died due to heart failure, the second cats died because of brain tumor and the third cat died due to an experiment gone wrong.

So there are none of the cats left out. All the cats died due to different reasons.

if you're asking what comes out, it's steam.