At what temperature does the numerical reading on a Celsius thermometer equal that on a Fahrenheit thermometer?

the temperature does the numerical reading on a Celcius thermometer equal that Fahrenheit is - 40°

Explanation:

°C = (°F - 32) / 1.8 ... (1)

⇒ °C = ° F ... (2)

replaicing (2) in (1):

⇒ °C = (°C - 32) / 1.8

⇒ 1.8 * °C = °C - 32

⇒ 1.8°C - °C = - 32

⇒ 0.8°C = - 32

⇒ °C = (-32 / 0.8)

⇒ °C = - 40°C