why is beta minus most commonly used for solving problems than beta plus(if =\- is not mentioned)

Beta-minus decay occurs in nuclei with an excess of neutrons, while beta-plus decay takes place in neutron-deficit nuclei. A lot of natural background radiation on Earth is due to fission or alpha-decay of heavy radioactive elements. The remains of fission or alpha-decay are neutron-rich nuclei, so beta-minus decay is more common on Earth.Whereas on stars beta-plus decay is typical, because neutron-deficit nuclei are produced in nuclear fusion.