TeX source:

\begin{array}{ll} c^{2}=a^{2}-b^{2} & \\ c^{2}=2304-529 & \text { Substitute using the values found in part (a). } \\ c=\pm \sqrt{2304-529} & \text { Take the square root of both sides. } \\ c=\pm \sqrt{1775} & \text { Subtract. } \\ c \approx \pm 42 & \text { Round to the nearest foot. } \end{array}