Answer
The object should be at $-40 (^oC \space or \space ^oF)$
Work Step by Step
The equation that relates the Fahrenheit and Celsius temperature scales is:
$5F - 9C = 160$
- Since we are looking for the temperature in which $F = C$, we are going to call a third unknown (T) that has exactly this value:
$F = C = T$:
$5T - 9T = 160$
$-4T = 160$
$\frac {-4T}{-4} = \frac{160}{-4}$
$T = -40$
