Respuesta :
					                   Mass number is # of protons + # of neutrons
since the atomic number is the number of protons, the number of protons is 57
so 168 = 57 + x
x = 111 neutrons
					                
					             since the atomic number is the number of protons, the number of protons is 57
so 168 = 57 + x
x = 111 neutrons
					                   Mass number is number of protons + number of neutrons 
168 - 57 = Answer
Answer = 111
					                
					             168 - 57 = Answer
Answer = 111
 
			                  