Solución

(2i×3j)×j=2(i×3j)×j=2(3)(i×j)×j=(6k)×j=6(i)=6i\begin{aligned} (2\bold{i}\times 3\bold{j})\times \bold{j} &= 2(\bold{i}\times 3\bold{j})\times\bold{j}\\ &= 2(3)(\bold{i}\times\bold{j})\times\bold{j}\\ &= (6\bold{k})\times\bold{j}\\ &= 6(−\bold{i})=−6\bold{i} \end{aligned}