The equivalent resistance seen between 'P' and 'Q' will be:

Concept:

The equivalent resistance is defined as a point where the total resistance is measured in a parallel or series circuit (in either the whole circuit or in a part of the circuit).

The equivalent resistance is defined between two terminals or nodes of the network. Equivalent resistance may sound complicated, but it’s just a technical way to say “total resistance”.

Analysis:

Simply the dotted region

(30 || 30) → (30× 30)/(30+30) = 15 Ω 

20||(15+5) = 20 || 20 = 10 Ω

(10+10) = 20 Ω 

Equivalent resistance = 10 + (20||20) = 10 + 10 = 20 Ω