Answer
$25^oC$
Work Step by Step
Substitute the given temperature value for $F$ in the given formula to obtain:
$\require{cancel}
C = \frac{5}{9}(77-32)
\\C=\frac{5}{9}(45)
\\C=\frac{5}{\cancel{9}}(\cancel{45}5)
\\C=25$
Thus, $77^oF = 25^oC$