Chapter 6 - Polygons and Quadrilaterals - 6-3 Proving That a Quadrilateral Is a Parallelogram - Practice and Problem-Solving Exercises - Page 374: 36

$AC = 7.47$

Theorem 6-8 states that in a quadrilateral that is a parallelogram, opposite sides are congruent. We can now deduce that $\overline{AC}$ is congruent to $\overline{PE}$. Therefore, if $AC = PE$ and $PE = 7.47$, then $AC$ also equals $7.47$.