Answer:
D) 4
Step-by-step explanation:
−9 + 12 + (unknown) + −8 = −1
Start by going through and testing each option
−9 + 12 + 2 + −8 =
3 + 2 + −8 =
5 + −8 =
−3
−3 ≠ −1
A) 2 is not possible.
−9 + 12 + −2 + −8 =
3 + −2 + −8 =
1 + −8 =
−7
−7 ≠ −1
B) −2 is not possible.
−9 + 12 + −4 + −8 =
3 + −4 + −8 =
−1 + −8 =
−9
−9 ≠ −1
C) −4 is not possible.
From this, D is looking like the answer. But to be sure, test it.
−9 + 12 + 4 + −8 =
3 + 4 + −8 =
7 + −8 =
−1
−1 = −1
D) 4 is the answer.