Answer
$R=21.4~\Omega$.
Work Step by Step
Given
$\frac{1}{R}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}$
$R=?, R_{1}=75\Omega, R_{2}=50\Omega,R_{3}=75\Omega$
$\frac{1}{R}=\frac{1}{75}+\frac{1}{50}+\frac{1}{75}$
Therefore, $R=21.4~\Omega$
How to use the calculator:
$75*x^{-1}+50*x^{-1}+75*x^{-1}=x^{-1}=$
