How do you go from 98 to 720 using just one letter?

Can you solve the below geography rebus by decoding the below rebus ?

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

There was a greenhouse.
Inside the greenhouse, there is a white house.
Inside the white house, there is a red house.
Inside the red house, there are lots of babies.

What is It?

Look at me. I can bring a smile to your face, A tear to your eye, Or even a thought to your mind. But, I can't be seen. What am I?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

I can write cow in 13 letters.

Can You?

The doctor prescribed you to take one pill from the bottle every half an hour. The bottle is now left with only three pills.

How long do you think you have before you run out of pills?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?