Question

A 2kg object weighs 19.6N on earth. If the acceleration due to gravity on mars is 3.71 meters per second what is the object mass on earth

Answer 1

The acceleration due to gravity at the Earth's surface is 9.8 m/s/s 

So a 2 kg object will accelerate at 9.8 m/s/s if it is dropped..... actually all dropped objects will accelerate at the same rate. 

The force of gravity on the object is given by Newton's 2nd Law 

F = m . a 

F = 2 . 9.8 = 19.6 N 

Now go to Mars , with a lower gravitational field strength. It only accelerates falling objects at 3.71 m/s/s 

So the force of gravity on the object is F = 2 . 3.71 = 7.42 N 

But the answer is (2) 2 kg, because the mass of the object stays the same and that is what you are asked for. 
Someone was trying to be tricky.