What brings you down but never up?

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

What is the coolest letter in the alphabet?

Which of the following words don't belong in the group and why?
CORSET, COSTER, SECTOR, ESCORT, COURTS

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

Three playing cards in a row. Can you name them with these clues? There is a two to the right of a king. A diamond will be found to the left of a spade. An ace is to the left of a heart. A heart is to the left of a spade. Now, identify all three cards.

A prisoner is told: "If you tell a lie, we will hang you and if you tell the truth, we will shoot you." What did the prisoner say to save himself?

Can you find the hidden animal in the picture below?

Prove that the below maths equation is true.

8 + 8 = 91