[kenny1999]

Actually I totally understand what Hess's law is and I know how to draw those Enthalpy Diagram, path....

However, I heard somebody say that there is a very very fast way or trick to do Hess's law problems (especially Mutiple choice questions), what you need is only a calculator, you don' even need to draw any Enthalpy diagram, path or write down anything to help  (of course, several equations as well as their enthalpy changes are given.)  I have been searching on the web for the related information but most of them uses those Hess's

thanks!