Find the value of "?" in the ball picture Riddle below:

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

There once were seven dwarfs who were all brothers. They were all born two years apart. The youngest dwarf is seven years old. How old is his oldest brother?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

How can you spell "White of an egg" in one word?
Hint: I know you can spell coke, poke, and joke.

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?