What is the word or phrase?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

What does this rebus mean?

O
N
C
E
TIME

Given that

(78)^9 = 6
And (69)^4 = 11

Can you find out

(99)^2 =?

(Note: This is Logical, not Mathematical)

By using 'because' continuously three times, can you make an English statement ?

John: "Hi Teacher, What is your favourite movie ?".
Chemistry Teacher: "Indium Cerium Platinum Iodine Oxygen Nitrogen".
Ten seconds later... John replied I got it.

Do you?

John, a 5-year-old boy, was really fond of the chocolates. He asked his Mother to give him some money to buy his favourite chocolates. His Mother gave him $45. He went to the shopkeeper and asked, "How much is one chocolate for?". The shopkeeper said $3 for one chocolate. Also, if you give me the wrappers of three chocolates, I will give you one for the exchange.
In total, how much chocolate could John eat?