Help pls it's about cells

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

If 90.0 grams of ethane reacted with excess chlorine,how many grams of dicarbon hexachloride would form

Joan writes four numbers on the board in standard form, and then she writes their scientific notation