What is the mass of a 3920 newton desk

mass of desk = 400 kg

Explanation:
The weight is defined as the gravitational force acting on a certain body.
It can be calculated as follows:
F = m * g
where:
F is the weight of the body = 3920 newton
m is the mass that we want to calculate
g is the gravitational force = 9.8 m/s²

Substitute with the givens in the above equation to get the value of the mass as follows:
3920 = mass * 9..8
mass = 400 kg

Hope this helps :)