$${(R_1 \parallel R_2) \times R_3 = \frac{11}{3}{}{\Omega},\quad (_R1 \parallel R_3) \times R_2 = \frac{11}{4}{}{\Omega},\quad (R_2 \parallel R_3) \times R_1 = \frac{11}{5}{}{\Omega}}$$