jmc

If $n$ is less than $3$, then $n+8$ is positive, $n-3$ is negative, and $n-12$ is negative. Therefore, the product on the left-hand side of the inequality is positive, so the inequality is not satisfied. If $n$ is strictly between 3 and 12, then $n+8$ is positive, $n-3$ is positive, and $n-12$ is negative. In this case, the product on the left-hand side is negative, so the inequality is satisfied. If $n$ is greater than 12, then $n+8$ is positive, $n-3$ is positive, and $n-12$ is positive. Again, the product is positive so the inequality is not satisfied. If $n=3$ or $n=12$, then the left-hand side is 0, so the inequality is not satisfied. Therefore, the only solutions of the inequality are the $12-3-1=\boxed{8}$ integers strictly between 3 and 12.