Answer
$4$ ohms
Work Step by Step
$a+b = 16, \frac{1}{a} + \frac{1}{b} = \frac{1}{3}$. Combining the second equation, $\frac{16}{ab} = \frac{1}{3}, ab = 48$. This yields the quadratic $x^2-16x+48$, which has the roots $x=4,12$, so the smaller resistance is $4$ ohms.
