The effective circuit is shown in the figure.
The resistance of arm EHG=10Ω+10Ω=20Ω,
will be parallel to resistance of arm EFG=10Ω+10Ω=20Ω.
Their effective resistance =20Ω+20Ω20Ω×20Ω=10Ω
Therefore, the equivalent resistance between A and D =5Ω+10Ω+5Ω=20Ω