Question

m3|l12 mm mix and match
keep going.
-9 + __ = 0
9 + __ = 0
12 + __ = 0
-12 + __ = 0
-12
-9
9
12

Explanation:

Step1: Solve for missing value

Let $x$ be the missing number. For $-9 + x = 0$, rearrange to isolate $x$:
$x = 0 - (-9) = 9$

Step2: Solve for missing value

Let $x$ be the missing number. For $9 + x = 0$, rearrange to isolate $x$:
$x = 0 - 9 = -9$

Step3: Solve for missing value

Let $x$ be the missing number. For $12 + x = 0$, rearrange to isolate $x$:
$x = 0 - 12 = -12$

Step4: Verify completed pair

For $-12 + 12 = 0$, this is already confirmed correct.

Answer:

$-9 + \boldsymbol{9} = 0$
$9 + \boldsymbol{-9} = 0$
$12 + \boldsymbol{-12} = 0$
$-12 + \boldsymbol{12} = 0$