Jenifer and Jesica are having a conversation.

Jenifer: I am definitely not over 30.
Jesica: I am 28 and you are surely 5 years older to me at least.
Jenifer: No, you are at least 29.

You are told that both of them are lying throughout in the conversation. Can you find their respective ages?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

What four weights can be used to balance from 1 to 30 pounds?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

What word begins and ends with an E, but has only one letter?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

I shave every day, but my beard stays the same. What am I?

Count the number of triangles in the below picture?

Can you write down eight eights so that they add up to one thousand?

Can you name an animal whose killing cannot be performed without spilling your own blood?