R2, R3 and R4 are in series and have resultant resistance R’ = 2 + 2 + 2 = 6Ω
R’ is in parallel combination with R1.

∴ Resultant resistance of the circuit (R)
\(\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}\)
\(\frac{1}{6}\) + \(\frac{1}{6}\)
Resistance R = \(\frac{6}{2}\) = 3Ω