#### Answer

$8.68$

#### Work Step by Step

Perform the subtraction first:
\begin{array}{ccc}
\require{cancel}
& & &\space 7\space3
\\&&&1\cancel{8}.\cancel{4}0
\\&- & &\underline{13.72}
\\&&&04.68
\end{array}
Add $4$ to the result to obtain:
$=4.68 + 4
\\=8.68$