Question

Element A has 15 protons. Determine the number of neutrons in its isotope with mass number 33.

Answer 1

Number of neutrons = Mass number - Number of protons
= 33 - 15 = 18

In short, Your Answer would be 18

Hope this helps!

Answer 2

18 neutrons.
Hope this is of help to you, and happy studying~!
~{Oh Mrs.Believer}