Can you replace the question mark with the correct number?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

What's the only room from which no one can enter or leave

Decode this picture on T-Shirt and tell what it says ?

At a party, there are five people and a whole round cake lying at the centre of the table. Only four people will make a cut and take their piece and the last one will get the remaining piece on the table. How can they make sure that everyone gets a 1/5th of the piece?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

In a science lab, a petri dish hosts a healthy colony of yeast for an experiment. Now every minute, all the yeast cells divide into two. At noon, there was just a single cell of yeast and at 1:22, the Petri dish was half full. Can you calculate when the dish will be full of yeast?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

What am I?

Can you identify if it's a murder or a suicide ?