Which describes the columbian exchange?

a.
the movement of plants, animals, diseases, and people among continents as a result of european exploration

b.
the migration of europeans to the americas after 1500

c.
columbus's plan for returning to the americas several times

d.
the trade between spanish explorers and native peoples in the americas

the migration of Europeans to the Americas after 1500 is the answer

Explanation:

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

travels along an axon. this triggers a wave of electrical activity that passes from the cell body along the length of the axon to the synapse