What is the pound mole of co2 ​

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Can someone me with questions 15 to 17 plz.

Which formula can be used to calculate the molar mass of ammonia (nh3)? molar mass of n + molar mass of h 3 × molar mass of n + molar mass of h molar mass of n + 3 × molar mass of h 3 × molar mass of n + 3 × molar mass of h