Element a has 15 protons . determine the number of neutrons in its isotopes with massnumber 33

Mass number= no. of protons+no. of neutron
no.of neutrons= 33-15=18

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

In an electrically neuteral atom, number of protons = number of electrons = atomic number.
Mass number = neutrons + protons/electrons/atomic number
Therefore,
neutrons = mass number - protons/electrons/atomic number
Neutrons = 33 - 15 = 18

The answer is thus B. But this is the solution and explanation along with it as proof.

Isotope of element A has a similar number of protons but different number of neutrons and atomic mass.
33-15= 18 neutrons

Mass number represents the sum of the protons and the neutrons.

Mass number = # protons + # neutrons

So, since we are given the mass number and the number of protons, we can plug those in to find the number of neutrons.

33 = 15 + ?

Number of neutrons is mass number minus number of protons. 
So the number of neutrons is 18.

33 - 15 = 18
This element is P-33 

18 i think

Explanation:

A=Z+N
A=mass number  (protons + neutrons)
Z=atomic number (number of protons).
N=number of neutrons.

Data:
Z=15
A=33

Then:

33=15+N
N=33-15=18

the number of neutrons in this element A will be 18.

Mass number - protons = neutrons

33 - 15 = 18

The number of neutrons here would be: 18