Answer
$Z = \frac{233}{37} + \frac{119}{37} i$
Work Step by Step
For $E=IZ$, where $I=7+5i$ and $E=28+54i$,
$(28+54i) = (7+5i)Z$
$Z = \frac{(28+54i)}{(7+5i)}$
$Z = \frac{(28+54i)(7-5i)}{(7+5i)(7-5i)}$
$Z = \frac{(196-140i+378i-270i^2)}{(49-25i^2)}$
$Z = \frac{(466+238i)}{74}$
$Z = \frac{233}{37} + \frac{119}{37} i$