Respuesta :

Remember this:

atomic mass= atomic number + number of neutrons 

The atomic number (same thing as number of protons) in this case is 15. The atomic mass is 31. 

So, we subtract 15 from 31 to find the number of neutrons.

31-15=16 

16 neutrons!!!

sorry i'm late:

16 (how to get answer is shown below on second photo):

Ver imagen SivethTheDragon
Ver imagen SivethTheDragon