Question

solve for all values of a in simplest form.
21 = |a + 28|

Explanation:

Step1: Consider positive case

$a + 28=21$

Step2: Solve for a in positive case

$a=21 - 28=-7$

Step3: Consider negative case

$a + 28=-21$

Step4: Solve for a in negative case

$a=-21 - 28=-49$

Answer:

$a=-7$ or $a = - 49$