How many neutrons does element x have if it's atomic number is 55 and it's mass number is 155?

What kind of action is a cause of air pollution

Lucia is walking barefoot in her yard. she accidentally steps on a nail. how will her nervous system work to generate a reaction? arrange the eventschronologically.

What are two ways that harvesting algae from the ocean may benefit human society? how might the harvest of algae negatively impact the ocean communities where that algae grows? how could this be prevented?