Answer:
First we need to write the general linear function as:
F = a*C + b
Second, we use the 2 first conditions and we have as a equations:
[tex]\left \{ {{86=30a+b} \atop {176=80a+b}} \right.[/tex]
Then, resolving the system of equations, we have:
a = 1.8 and b = 32
A) So the linear function is:
F = 1.8*C + 32
B) So in this case we reverse the equation as follow:
[tex]F - 32 = 1.8C\\\\\frac{F-32}{1.8} = C[/tex]
Finally we have:
[tex]C = \frac{F-32}{1.8}[/tex]
C) In this case, we consider F = C and we have:
[tex]C = 1.8C+32\\C = -40[/tex]
So
C = F = -40degrees