Question

What is the value of a in the following equation: -a = 3a + 8?

Answer 1

$-a = 3a + 8$

Add $-3a$ to both sides

$-4a = 8$

Divide both sides by $-4$

$a = -2$

Choice C.

Check:

$3a + 8 = 3(-2) + 8 = 2 = -a \quad \checkmark$ 

Answer 2

The correct answer is:  [C]:  "-2 " . 
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                →  " a = - 2 " .
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Explanation:
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Given:  " -1a = 3a + 8 " ;  Solve for "a" .

Add "1a" to each side of the equation:

→  " -1a + 1a = 3a + 1a + 8 ; 

to get:  0 = 4a + 8 ; 

↔  4a + 8 = 0 ;

Subtract "8" from each side of the equation:

→  4a + 8 − 8 = 0 − 8 ; 

to get:

→  4a = - 8  ; 

Divide each side of the equation by "4" ; 
   to isolate "a" on one side of the equation; & to solve for "a" ; 

→  4a / 4  = -8 / 4 ; 

to get:

→  a = -2 . 
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The answer is:  " a = -2 " .
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