$\def\arraystretch{1.25} \begin{array}{l}\,\, \,\, 12345 : 15 = 823 \\\underline{-120}\\\,\,\,\,\,\,\,\,\,\,\,3\color{#ff6600}{4} \\ \,\,\,\,\,\,\, \underline{-30} \\\,\,\,\,\,\,\,\, \,\,\,\,\,\,\,4\color{#ff6600}{5} \\\, \,\,\,\,\,\,\,\,\,\underline{-45} \\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0\end{array}$