Answer
$-20^oC$
Work Step by Step
Substitute the given temperature value for $F$ in the given formula to obtain:
$\require{cancel}
C = \frac{5}{9}(-4-32)
\\C=\frac{5}{9}(-36)
\\C=\frac{5}{\cancel{9}}(\cancel{-36}-4)
\\C=-20$
Thus, $-4^oF = -20^oC$
