21f

This is the conversion formula for Fahrenheit to Celsius, where TF is temperature in Fahrenheit and TC is temperature in Celsius.

TC=59⋅(TF-32)

Substitute the Fahrenheit temperature into the formula.

TF=59⋅(21-32)

Subtract 32 from 21.

Tc=59⋅-11

Combine 59 and -11.

Tc=5⋅-119

Multiply 5 by -11.

Tc=-559

Tc=-559

Move the negative in front of the fraction.

Tc=-559

Convert the fraction to a decimal by dividing the numerator by the denominator.

Tc=-6.1‾

Convert to Celsius 21f