Answer
$5$
Work Step by Step
With $x=20,$ the statement, "y is $4$ less than half of $x$ results to
\begin{array}{l}\require{cancel}
y=\dfrac{1}{2}(20)-4
\\\\
y=10-4
\\\\
y=6
.\end{array}
With $x=20$ and $y=6,$ the given expression, $
\dfrac{5y-x}{2}
,$ evaluates to
\begin{array}{l}\require{cancel}
\dfrac{5y-x}{2}
\\\\=
\dfrac{5(6)-20}{2}
\\\\=
\dfrac{30-20}{2}
\\\\=
\dfrac{10}{2}
\\\\=
5
.\end{array}
