Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Prove that the below maths equation is true.

8 + 8 = 91

Can you replace the X (both small and big x) with the numbers between 1 to 19 such that all the rows of 3 numbers between X (big x) sum to 23?

What demands an answer, but asks no questions

It belongs to you, but other people use it more than you do. What is it?

What is the next number in the series?

15 29 56 108 208 ?

I look at you, you look at me, I raise my right, you raise your left. What am I?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?