Questions

The logic in this puzzle is summing the result of [subtraction of upper two digits] & [addition of lower two digits] 

Hence, the result is  

(5 - 3) + (2 + 8) = 2 + 10 = 12.

Natural gas is primarily composed of methane, but also contains ethane, propane, and heavier hydrocarbons.

Natural gas is a colorless, tasteless, odorless, and non-toxic gas. Because it is odorless, mercaptan is added to the natural gas, in very small amounts to give the gas a distinctive smell of rotten eggs. This strong smell can alert you of a potential gas leak.

It also contains small amounts of nitrogen, carbon dioxide, hydrogen sulphide and trace amounts of water.

Moscow 37o and Los Angeles 118oW show a longitude difference of 155o across the Atlantic and of 205o across the Pacific.

Central Processing Unit is the main part of the computer.

CPU chip or main processor is that part in the computer which performs or executes all the instructions or programs.