Answer
Option (D);
$x=\left\{\frac{1}{3}, 7\right\}$
Work Step by Step
RECALL:
The zero-factor property states that if $ab=0$, then either $a=0$ or $b=0$ or both are zero.
Among the given equation, the one in Option (D) is set up for direct use of the zero-factor property.
Using the property gives:
\begin{array}{ccc}
&3x-1=0 &\text{or} &x-7=0
\\&3x=1 &\text{or} &x=7
\\&x=\frac{1}{3} &\text{or} &x=7
\end{array}
Thus, $x=\left\{\frac{1}{3}, 7\right\}$.
