Solution
= Solution
Compare with $(\mathbf b\times\mathbf a)_i=\epsilon_{ijk}b_ja_k$. The scalar factors commute, so the answer is
$$
\boxed{\mathbf b\times\mathbf a=-\mathbf a\times\mathbf b.}
$$
The order of the contracted indices matters because the <Levi-Civita symbol> is antisymmetric.