Answer
$$
\frac{9}{5} C +32, \ \ -4
.$$
Work Step by Step
To solve the given equation for $ F$, we multiply both sides by $\frac{9}{5}$ and then we simplify as follows:
$$
C= \frac{5}{9}(F-32) \Longrightarrow \frac{9}{5} C=\frac{9}{5} \frac{5}{9}(F-32) \Longrightarrow \frac{9}{5} C =F-32 \\ \Longrightarrow F=\frac{9}{5} C +32
.$$
Now, by substitution, we have
$$
F=\frac{9}{5} C +32=\frac{9}{5} (-20) +32=-4
.$$
