Can you find the key in the picture below?

Can you solve the maths in the below-given picture equation?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.

Next Number in the Series,

5, 16, 49, 104, ?

What word begins and ends with an E, but has only one letter?

What's a single-digit number with no value?

A generous owner of a company decided to give a bonus of $45 to every man and $60 to every woman on his birthday. But only one-ninth of the men and one-twelfth of the women were present to take the bonus.

Can you calculate the amount of money the owner spent if there were 3552 employees?

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.

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10