Answer
$160^\circ $C
Work Step by Step
We know that
$$F = \frac{9}{5}\times C +32.$$ Given that $F = 2C$, we have: $$\begin{aligned}
2C& = \frac{9}{5}\times C +32\\
10C&=9C+160\\
C& = 160.
\end{aligned}$$ The temperature should be $160^\circ $ C or $320^\circ $F.
