Answer
$x=3$ or $x=-4$.
Work Step by Step
Rewrite the equation in the form
$$x^2 + x -12=0.$$
By factorization, we have
$$x^2 + x -12=(x-3)(x+4)=0.$$
Then we have
$$(x-3) =0, \quad \text{or} \quad (x+4)=0$$
That is,
$x=3$ or $x=-4$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.