Answer
One way to complete the magic square would be:
8 -3 -2
-5 -1 9
0 7 -4
Work Step by Step
$8 + (-3) + (-2) = 3$
$(-5) + (-1) + 9 = 3$
$0 + 7 + (-4) = 3$
$8 + (-5) + 0 = 3$
$(-3) + (-1) + 7 = 3$
$(-2) + 9 + (-4) = 3$
$8 + (-1) + (-4) = 3$