Answer:
Mass is a constant value and will not change no matter if you are in space with no gravity, or on the sun.
Mass is the amount of matter that one thing has and is made up of.
Therefore it doesn't matter where you are, mass will always stay constant.
Therefore if someone weighs 70kgs, their mass is 70kg.
Weight is dependent on where they are and is the amount of force that one pushes up on the earth from.
The formula for weight is w = mg
Weight = mass • the acceleratory force of gravity.
G for earth is = -9.82 m/s^2
So, weight would equal:
70 • 9.82 = 687.4 Newtons
Knowing this, why is weight the same on top of the mountain and on the bottom? Since the we are still on earth, there is a constant force of gravity. As long as you are on earth, then you will constantly accelerate into the center of earth at a rate at -9.82 m/s^2, therefore the measurement of weight will always be the same.
Hope this helped :)