Studying the weak nuclear response, especially the Gamow-Teller (GT) transitions starting from stable as well as unstable nuclei is one of the key issues in nuclear and nuclear-astrophysics.We studied the GT transitions by means of hadronic (3He; t) charge-exchange reactions and complementary decays. Owing to the simple nature of the operator that causes GT transitions, information on the crucial and critical part of the nuclear structure can be studied. Under the assumption that isospin is a good quantum number, symmetry is expected for the structure of mirror nuclei and the GT transitions starting from them. The results from -decay studies and the strength distribution of GT transitions from the (3He; t) reaction are compared and also combined for the understanding of nuclear structure of far-from-stability nuclei.