Complete the table series riddle by finding the number that can replace "??".

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

A man died, leaving $10,000,000 for his widow, 5 sons and 4 daughters. Each daughter received an equal amount, each son received twice as much as a daughter, and the widow received three times as much as a son.

How much did the widow receive?

Which five letter word can be added at the end of below word to form a
valid word?

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What does below chemistry rebus means?

John is 45 years older than his son Jacob. If you find similarities between their ages, both of their ages contain prime numbers as the digits. Also, John's age is the reverse of Jacob's age.

Can you find their ages?

A sea diver is a real show-off. He showed everyone that he can hold his breath underwater for 15 minutes.

I went to the diver and told him that I can be underwater for double the time i.e 30 minutes.
He responded that he will give me 100$ if I would be able to do it. I won 100$.

What did I do?

I have eight fingers and two thumbs but I do not live. What Am I?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

What goes through cities and fields, but never moves?