Nilai hambatan penggantinya adalah..

Rs =8 ohm + 4 ohm = 12 ohm (hambatan seri)
=1/Rp = 1/12 ohm + 1/rs (hambatan paralel)
=1/Rp = 1/12 + 1/12
=1/Rp = 2/12 atau 1/6
=Rp = 6 ohm

6ohm maap salah ye bro