This study investigates the preparation of superconductor samples of Bi_2−xAg_xBa_2−ySr_yCa₂CO₂Cu₃O_10+δ using the solid-state reaction method with partial substitution of silver in both Bi and Ba at ratios of x = 0, 0.15, 0.25 and y = 0, 0.15, 0.25. X-ray diffraction is used to analyse the crystal structure, revealing a tetragonal structure with an increase in the c-axis length at an Ag substitution ratio of x = 0.15. Electrical-resistivity and critical-temperature (T_c) measurements are conducted using four-probe methods, showing an increase in T_c with Ag substitution up to x = 0.15, where T_c values reach 137.7 K and 162.5 K for the Ag-substituted samples. As observed, the oxygen content δ has a direct correlation with T_c, increasing as T_c improves. These results provide valuable insights into enhancing the properties of high-temperature superconductors through chemical substitutions and oxygen distribution, with promising implications for future applications in energy systems and magnetic-transportation technologies.