Answer
Megan was $7$ under par.
Work Step by Step
The term "over" suggests the addition of a par while the term "under" suggests the subtraction of a par during the tournament.
These are the rounds shot by Megan:
$+3$, $-2$, $-3$ and $-5$
Add the rounds up:
$= (+3) + (-2) + (-3) + (-5)$
$= 3 - 2 - 3 - 5$
$= 3 - 5 - 5$
$= 3 - 10$
$= -7$
Therefore, Megan was $7$ under par.