Answer: The number of neutrons in given isotope are 10
Step-by-step explanation:
Atomic number is defined as the number of protons or electrons that are present in a neutral atom.
Atomic number = number of protons = number of electrons
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons
The isotopic representation of an atom is:

where,
Z = Atomic number of the atom
A = Mass number of the atom
X = Symbol of the atom
We are given:
An isotope having formula:

Atomic number = Number of protons = 8
Mass number = 18
Number of neutrons = 18 - 8 = 10
Hence, the number of neutrons in given isotope are 10