You're missing the fact that each comparison has to be complete. If you say (x > 10 || x == 5) the compiler know what you mean. If you say (x >10 || == 5) it doesn't. The compiler doesn't remember the x and guess that it is supposed to apply to the next comparison too.
To check if you're talking sense try putting parentheses round each comparison ((x>10) || (==5)). The ==5 on it's own makes no sense at all. What is supposed to be equal to 5? You haven't said.
Steve