Answer
The equivalent resistance is $~~6.67~\Omega$
Work Step by Step
If we imagine that a battery is connected between A and B, the current could flow across the left resistance, or the middle resistance, or the right resistance. Therefore the three resistances are in parallel.
We can find the equivalent resistance:
$\frac{1}{R_{eq}} = \frac{1}{20.0~\Omega}+\frac{1}{20.0~\Omega}+\frac{1}{20.0~\Omega}$
$\frac{1}{R_{eq}} = \frac{3}{20.0~\Omega}$
$R_{eq} = \frac{20.0~\Omega}{3}$
$R_{eq} = 6.67~\Omega$
The equivalent resistance is $~~6.67~\Omega$
