#### Answer

$-\dfrac{1}{72}$

#### Work Step by Step

Using order of operations, the given expression, $
\left(\dfrac{1}{3}\right)^2-\left(\dfrac{1}{2}\right)^3
,$ simplifies to
\begin{array}{l}\require{cancel}
\dfrac{1}{9}-\dfrac{1}{8}
\\\\=
\dfrac{8}{72}-\dfrac{9}{72}
\\\\=
\dfrac{8-9}{72}
\\\\=
\dfrac{-1}{72}
\\\\=
-\dfrac{1}{72}
.\end{array}