What purpose did the gates in the wall serve? A. To allow trade and necessary contact with northern people
B. To allow the emperor to go in and out
C. To allow the northern people to go in and out
D. To allow the army to go in and out

b or d sorry i cant be a better help

Explanation:

sorry for the late response  

hello,

your answer whould be d

8 - (2a + 7) = a + 40     distribute/multiply - into (2a + 7)

8 - 2a - 7 = a + 40

1 - 2a = a + 40       add 2a on both sides

1 = 3a + 40         subtract 40 on both sides

-39 = 3a       divide 3 on both sides

-13 = a

[proof]

8 - (2a + 7) = a + 40

8 - (2(-13) + 7) = -13 + 40

8 - (-26 + 7) = 27

8 - (-19) = 27

8 + 19 = 27

27 = 27