Which statement about the battle of antietam is true?

a.
it convinced president abraham lincoln that general george b. mcclellan had to be removed.

b.
it was a decisive victory for general robert e. lee.

c.
it caused fewer deaths than other major battles.

d.
it forced president abraham lincoln to delay the emancipation proclamation.

It's A.

Explanation:

a. because the u.s. was the leading with the most technology, economy, etc. also was teamed with other allies witch boosted the economy and materials to improve technology and use it.

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