Question 954208
You have two data points, (F,K).  They are (212,373) and (32,273).  


K as a function of F:
{{{K=((373-273)/(212-32))F+b}}} in slope-intercept form.
{{{b=K-mF}}}
Pick a point...
{{{b=273-((373-273)/(212-32))*32}}}


Evaluate b, substitute it into the first equation for K and simplify.
{{{m=10/18=5/9}}}
-
{{{b=273-(5/9)*32}}}
{{{b=255.2}}}


{{{highlight(K=(5/9)F+255.2)}}}


Inverse?
{{{y=(5/9)F+255}}}
switch:  {{{F=(5/9)y+255}}}
{{{F-255=(5/9)y}}}
{{{(F-255)(9/5)=y}}}
y is the inverse of K.
{{{y=K^-1=(9/5)F-255*(9/5)}}}
{{{highlight(y=K^(-1)=(9/5)F-459.4)}}}, but unsure of the practical meaning.