The three resistance of 20 ohm, and 10 ohm and 20 ohm on the extreme right side are in series.
So, the resultant of these three resistances = 20+20+10 = 50 ohms
This 50 ohms is in parallel with 30 ohms. So resultant of these two will be
1/R = 1/30 +1/50
1/R = 80/1500
R = 18.75 ohms
Now, the resistances 10 ohms, 18.75 ohms and 10 ohms are in series.
Therefore, resultat resistance = 18.75 + 10+ 10 = 38.75 ohms.
