\def\XBOXSHIFT{2.5mm}
\def\YBOXSHIFT{-2mm}
\def\BOXRULE{1pt}

\newtcolorbox{solutionBox}{enhanced,
  title=Solution,%
  coltitle=black,%
  colback=white,%
  colframe=black,%
  sharp corners,%
  attach boxed title to top left= {xshift=\XBOXSHIFT,yshift=\YBOXSHIFT},%
  boxrule=\BOXRULE,%
  boxed title style={boxrule=\BOXRULE, colframe=black, colback=white, sharp corners}%
}%
\newtcolorbox{breakableSolutionBox}{enhanced,breakable,%
  title=Solution,%
  coltitle=black,%
  colback=white,%
  colframe=black,%
  sharp corners,%
  attach boxed title to top left= {xshift=\XBOXSHIFT,yshift=\YBOXSHIFT},%
  boxrule=\BOXRULE,%
  boxed title style={boxrule=\BOXRULE, colframe=black, colback=white, sharp corners}%
}%