Answer
$C = \frac{5}{9}~(F-32)$
Work Step by Step
The formula used to convert from Celsius to Fahrenheit is as follows:
$F = \frac{9}{5}C+32$
We can solve this formula for C to derive the formula used to convert from Fahrenheit to Celsius.
$F = \frac{9}{5}C+32$
$F-32 = \frac{9}{5}C$
$5~(F-32) = 9~C$
$\frac{5}{9}~(F-32)=C$
$C = \frac{5}{9}~(F-32)$
