Answer:
15 neutrons
Step-by-step explanation:
the atomic mass shows the amount of neutrons and protons added together
the atomic number shows us how many protons they are (you can also find out how many electrons a element has by looking at its atomic number as it will have the same amount of protons)
so to find the amount of neutrons the sample has you have you subtract the atomic number which is the amount of protons from the mass number which tells us the amount of neutrons and protons added together but we only need the neutrons that's why we subtract it
33-18=15