Step-by-step explanation:
The question is not complete, as the information, your best friend in Europe about the temperature over there is missing, nevertheless, we can proceed with this problem by plugging in an assumed temperature.
The expression for conversion from degrees F to degrees C is given as
T(°C) = (T(°F) - 32) × 5/9
Now say temperature your friend e-mailed you is 68 degrees Fahrenheit (you can as well plug in your own value)
T(°C) = (68°F - 32) × 5/9
T(°C) = (36) × 5/9
T(°C) = 180/9 = 20 °C
T(°C) = 20 °C
The geometric mean is √24 * 32 = √768 = 16√3.