Even under the most ideal conditions, only about 8% of the internal energy of the steam produced in a steam engine can be converted into actual work. what happens to the other 92% of the steam's available energy?

As per the law of conservation of energy, no energy is created or destroyed. Therefore, we can conclude that the remaining 92% of energy released in electricity generation from steam power plants is converted to other, non-utilizable forms of energy. Such forms include sound energy or thermal energy between the moving parts of the plant.

No because a circle or pie graph usually shows percentages you'd need a line graph