Answer
$ad-bc=-\dfrac{3}{8}$
Work Step by Step
Substituting $
a=2
,$ $
b=\dfrac{1}{2}
,$ $
c=\dfrac{1}{4}
,$ $
d=-\dfrac{1}{8}
$ in the expression $ad-bc,$ then
\begin{align*}\require{cancel}
&
\left( 2 \right)\left( -\dfrac{1}{8} \right)-\left( \dfrac{1}{2} \right)\left( \dfrac{1}{4} \right)
\\\\&=
-\dfrac{2}{8}-\dfrac{1}{8}
\\\\&=
-\dfrac{3}{8}
.\end{align*}
Hence, $
ad-bc=-\dfrac{3}{8}
$.
