Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

Using mathematical symbols like +, -, and x in order to make the equations correct. Replace # with the above-given symbols.

9 # 8 # 7 # 6 # 5 # 4 = 91

What has a bottom at the top?

Replace the question mark with the correct number below.

What number comes next in the series?

5 15 5 18 5 24 14 20 _

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

You are provided with a grid (as shown in the picture). Can you fill the squares with numbers 1-8 in a manner that none of the two consecutive numbers are placed next to each other in any direction (vertically, horizontally or diagonally?)

If,

A = 1

B = 2

C = 3

...

...

Z = 26.

Based on above rule, you need to find an eleven letter word whose letter sum is equal to 52.

You board a train. The train will have to enter a tunnel soon. You are claustrophobic. Which place is the best for you to sit?

If eleven plus two equals one, what does nine plus five equal?