Answer: The number of neutrons in the given isotope are 27.
Step-by-step explanation:
Atomic number is defined as the number of electrons or number of protons that are present in a neutral atom. It is represented as Z.
Z = Atomic number = Number of electrons = Number of protons
Mass number is defined as the sum of number of protons and number of neutrons present in an atom. It is represented as A.
A = Mass number = Number of protons + Number of neutrons
Number of neutrons = Mass number - Atomic number
We are given an isotope having representation:

Atomic number or number of protons = 20
Mass number = 47
So, number of neutrons = 47 - 20 = 27
Hence, the number of neutrons in the given isotope are 27.