[tex] \sf \: The \: value \: of \: x \: is \: the \: number \: that \: belongs \: to \: the \: solution \: \\ \sf \: set \: of \: the \: equation. \: So \: we \: need \: to \: find \: x.[/tex]
[tex] \sf \: x + 3 = 45 \\ \sf \: x = 45 - 3 \\ \sf \: x = \underline{42}[/tex]
Answer ⟶ [tex]\boxed{\bf{D.42}}[/tex]
