Math Help - Lie algebras question

1. Lie algebras question

The problem:

$L$ a Lie algebra. Let $H \lhd L$ and $K \leq L$. Then prove that $H+K := \{ h+k : h \in H, k \in K\}$ is a subalgebra of $L$.

Never mind - I was attempting to show it was an ideal, not a subalgebra. Is it possible to delete posts?