To solve $${\mathtt{84}}{\mathtt{\,-\,}}\left[{\mathtt{8}}{\mathtt{\,-\,}}{\left(-{\mathtt{2}}\right)}^{{\mathtt{3}}}\right]$$, first do the exponents.
$${\left(-{\mathtt{2}}\right)}^{{\mathtt{3}}} = \left(-{\mathtt{8}}\right)$$
Now, subtract $$\left(-{\mathtt{8}}\right)$$ from $${\mathtt{8}}$$.
$$8-(-8)=$$ $${\mathtt{8}}{\mathtt{\,\small\textbf+\,}}\left({\mathtt{8}}\right) = {\mathtt{16}}$$
Finally, subtract $${\mathtt{16}}$$ from $${\mathtt{84}}$$.
$${\mathtt{84}}{\mathtt{\,-\,}}{\mathtt{16}} = {\mathtt{68}}$$
So, $${\mathtt{68}}$$ is our final answer.
Hope this helps!
