if a man weighs 60 kg on earth, then how far must he go from the center of the earth so that he weighs 30 kg? could i know the steps to do this problem.

Here, it is given that- 'A man weighs 60 kg on earth'; now kg is the unit of mass and not weight.

Now, mass of a body is proportional to the quantity of matter contained in the body and independent of acceleration due to gravity. Therefore, the mass of the body does not change with depth/height and hence it will be 30 kg nowhere.