## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$15$
$\bf{\text{Solution Outline:}}$ To evaluate the given expression, $x+y ,$ substitute the given values $x=3$ and $y=12.$ $\bf{\text{Solution Details:}}$ Substituting $x=3$ and $y=12,$ the given expression evaluates to \begin{array}{l}\require{cancel} x+y \\\\= 3+12 \\\\= 15 .\end{array}