Why was the aqueduct
considered one of Rome's
greatest achievements?

Aqueducts

First developed around 312 B.C., these engineering marvels used gravity to transport water along stone, lead and concrete pipelines and into city centers. Aqueducts liberated Roman cities from a reliance on nearby water supplies and proved priceless in promoting public health and sanitation.

Explanation:

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

social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they liv