In terms of naming organic compounds, always identify the longest parental chain in the molecule first.
For the first it would have 3 carbons
Next number the carbons to give you the substituents the quickest.
For instance for number 1, it does not matter, but for number 2, you would start numbering the carbons from the left compared to the right, because if you number from the left
The methyl group appears immediately after, on 2nd carbon, but if you number from the right, it appears on the 3rd.
Always number to give the lowest position or numbering of the substituents.
