2, 3, 5, 9, 17, _ What is the next number in the sequence?

How many triangles are there in the picture below?

On her drawing table, Sayna lit 12 coloured candles. A few seconds later she blew two candles off.

How many candles Sayna have at the end?

What's a single-digit number with no value?

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

I ask Joseph to pick any 5 cards out of a deck with no Jokers.

He can inspect then shuffle the deck before picking any five cards. He picks out 5 cards then hands them to me (Jack can't see any of this). I look at the cards and I pick 1 card out and give it back to Joseph. I then arrange the other four cards in a special way, and give those 4 cards all face down, and in a neat pile, to Jack.

Jack looks at the 4 cards i gave him, and says out loud which card Joseph is holding (suit and number). How?

The solution uses pure logic, not sleight of hand. All Jack needs to know is the order of the cards and what is on their face, nothing more.

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

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

What is the word or phrase?