HIJKLMNO What well known formula does this represent?The answer is below, written backwards. 

 

.O ot H- O2H - retaw rof alumrof ehT 

When one does not know what it is, then it is something; But when one knows what it is, then it is nothing. What is it? The answer is below, written backwards. 

 

.elddir A 

What do cows give after earthquakes? Warning-this is a kind of pun!The answer is below, written backwards. 

 

.sekahs kliM 

Why were outlaws the strongest men in the old (American ) west? Caution- this is a pun.The answer is written below, backwards. 

 

.sniart pu dloh dluoc yehT 

Why did the robot go to a psychiatrist? The answer is below, written backwards. 

 

.esool wercs a dah tI 

Why is "h" the most popular letter of the alphabet?The answer is below , written backwards. 

 

.yadiloh yreve fo trats eht si tI