What famous saying does this rebus mean?

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A few friends are enjoying their sea voyage in a boat full of apples. On the way, they felt hungry and thus decided to eat the apples. Together, they ate two dozen of apples. When they have eaten the apples, will there be any change in the water level?

I’m tall when I’m young, and I’m short when I’m old. What am I?

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

There is an English word that can be used up to four times in a row without modifying the spelling and form a valid grammatical sentence.

Do you know what word is that?

How many times can you subtract the number two from the number fifty?

A man embarked on a questionnaire game. He kept asking the same question to whomever he found. The answer each time was different.

Can you guess what the question was?

What is always in front of you but can’t be seen?

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

Replace the question mark with the number below given a simple math problem.