Step-by-step explanation:
A lot of the names you're just going to have to look up/know. CH4 is methane, which you would just have to know.
As for the molar mass, for each compound you have to add up the masses of each atom. Using CH4 as an example, you would have to add the mass of the carbon atom with the 4 hydrogen atoms. Using a periodic table you can see that the mass of carbon is about 12.0107 g and the mass of each hydrogen atom is about 1.008 g.
12.0107 + (4 x 1.008) = 16.0427 g
Just be careful with compounds such as Ca3(PO4)2, because there are 2 phosphorous atoms and 8 oxygen atoms.
For percent composition you have to find how much each element within the compound makes up the compound's mass. Since you will have already calculated the molar mass, you can add up the mass of a particular element within a compound and divide it by the compound's molar mass. Then multiply by 100 to get the percent.
For CH4,
Carbon:
(12.0107/16.0427) x 100 = 74.87 %
Hydrogen:
(4 x 1.008/16.0427) x 100 = 25.13 %