Find the next number in the series below

21 32 54 87 131 ?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

1. Where does Easter come from before Valentine's Day?

2. Do you know what is in the middle of Valentine's?

3. What did the lady bee say to the man bee on the occasion of Valentine's Day

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

You need to move three matchsticks to form three squares. Can you do it?

Count the squares in the matchstick puzzle below?

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?