The temperature which has same numerical value on Celsius and Fahrenheit scale is

Let $T$ be the same numerical value of temperature on Celsius scale and Fahrenheit scale. Then using the relation

$\frac{°C}{100}=\frac{°F-32}{180}$

According to question, $°C=°F=T$

$\therefore \frac{T}{100}=\frac{T-32}{180} \therefore T=-40°C=-40°F$