How many neutrons does element x have if its atomic number is 25 and its mass number is 92?

Atomic mass is the sum of neutrons and protons, and atomic number is the number of protons.
Therefore, 92-25 = 67.

67 neutrons.

Sidenote:
Electrons are not considered in atomic mass since they weigh way too little

Atomic mass is the sum of neutrons and protons, and atomic number is the number of protons.
Therefore, 92-25 = 67.

67 neutrons.

Sidenote:
Electrons are not considered in atomic mass since they weigh way too little