3, 5, 15, x, 51, 53,159, 161

• 15 and x are related as 15+2=17( see next two )
  
  51 and 53 are related as 51+2=53
  159 and 161 are related as 159+2=161
  so x=17
• 12 years agoHelpfull: Yes(4) No(0)
• 159-161=2
  53-51=2
  x-15=2
  x=17
• 12 years agoHelpfull: Yes(2) No(2)
• ANSWER : 15
  
  SOLUTION :
  
  51+2=53
  159+2=161
  So,
  15+2=17
• 12 years agoHelpfull: Yes(2) No(1)
• 17
  161-159=2,53-51=2.so,diff s 2.we get 15+2=17
  
• 12 years agoHelpfull: Yes(1) No(0)
• 17 because the even position are the thrice of d previous number and the odd position (starting from 3rd position) are two more than d prev one
• 12 years agoHelpfull: Yes(0) No(0)
• 3*5=15
  15+2=17
  17*3=51
  51+2=53
  53*3=159
  159=2=161
• 12 years agoHelpfull: Yes(0) No(0)