According to the question,
(a) R1 = 3 + 3
R1 = 6 ohm
R2 = 3 ohm
R1 and R2 are joined in parallel
1 / R = 1 / R1 + 1 / R2
1 / R = 1 / 6 + 1 / 3
1 / R = (1 + 2) / 6
1 / R = 3 / 6
1 / R = 1 / 2
R = 2 ohm
(b)So since, R = 2 ohm
R3 = 3 ohm
R4 = 3 ohm
R’ = R + R3 + R4
R’ = 2 + 3 + 3
R’ = 8 ohm