As this is problem based on symmetrical arrangement of the resistors. The resistor which is working as a bridge between the two triangular shapes is having same environment(i.e. symmetrical voltage and current points on it) hence this can be divided into two parts having 1/2 ohm resistance. After that this problem remains only of some combinations of series and parallel connected resistors, which can be easily solved by basic formulas. Final answer is 8/7 ohm.