What does below chemistry rebus means?

Can you circle exactly four of these numbers such that the total is twelve?

1 6 1
6 1 6
1 6 1
6 1 6

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

Rectify the following equality 101 - 102 = 1 by moving just one digit.

81 x 9 = 801. What must you do to make the this equation true?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

I am sure no one can have two things for dinner. what are they?

It is deaf, Dumb and Blind!!!

Still, always tells the truth. What is it?

Identify the hidden meaning behind this picture?

A man hijacks an aeroplane transporting both passengers(8 of them) and valuable cargo. After taking the cargo, the man demands nine parachutes, puts one of them on, and jumps, leaving the other eight behind. Why did he want eight?