From my poor drawing , it's obvious that the resistance between A and B terminal is just
$$((((((100 || 100)+30) ||80)+20)||60)+20) = 50\Omega$$
But I am getting confused about determining the Thevenin voltage across the AB terminal.
If I remove the \$50\Omega\$ resistance from AB then I can ignore the rightmost \$20\Omega\$ resistor as no current is passing through it.
Then the equivalent resistance for the circuit would be (across the 80V source) $$((((60+20)||80)+30||100)+100) = 141.176\Omega$$
So, the current through the leftmost \$100\Omega\$ resistor is \$80/141.176 = .567\$A.
Then the current through the \$30\Omega\$ resistor is \$.567 \times 100/130 = .436\$ A and the current through the \$60\Omega\$ one is \$.436/2 = .218\$A. But then the \$V_{\text{TH}} = V60 = 60 \times .218 \text{V} = 13 \text{V}\$.
But the actual answer in my book is 10 V. What am I doing wrong here?
Source: It's an example problem from "V.K Mehta - Principles of Electronics".