what does the below math rebus puzzle mean?

How many letters are in the alphabet?

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

What is the largest number you can write with just 3 digits?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

The following four words might seem abrupt to you. But you can make them meaningful by just adding vowels.
RDSH
GGPLNT
TMT
NN

Hint: All of them are vegetables.

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

You need to remove two matchsticks to make the below equation true. Can you do it ?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?