The weight is the product of the mass of the body and the gravity acceleration :
(1)
Where is the acceleration due gravity with a value of for the Earth
If we want to find the mass, we have to find in equation (1):
(2)
(3)
Finally:
6.2m questions
8.1m answers
of the body and the gravity acceleration 
: 
(1) is the acceleration due gravity with a value of 
for the Earth in equation (1): 
(2) 
(3) 