How have the steppes of Central Asia influenced history? Steppes contribute to the development of cities.
The steppes were a natural barrier against invaders.
Steppes encourage a nomadic lifestyle with unstable government.
Steppes are mostly barren since people do not wish to live there.

is that it?

explanation:

what are the choices?

simplify brackets

8 - 2a - 7 = a + 40

simplify 8 - 2a - 7 to -2a + 1

-2a + 1 = a + 40

add 2a to both sides

1 = a + 40 + 2a

simplify a + 40 + 2a to 3a + 40

1 = 3a + 40

subtract 40 from both sides

1 - 40 = 3a

simplify 1 - 40 o -39

-39 = 3a

divide both sides by 3

-39/3 = a

simplify 39/3 to 13

-13 = a

switch sides

a = -13