$${\mathtt{7}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{12}} = {\mathtt{29}}$$
$${\mathtt{4\,785}}{\mathtt{\,\small\textbf+\,}}{\mathtt{321}}{\mathtt{\,\small\textbf+\,}}{\mathtt{204}} = {\mathtt{5\,310}}$$
$${\mathtt{7}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{12}} = {\mathtt{29}}$$
$${\mathtt{4\,785}}{\mathtt{\,\small\textbf+\,}}{\mathtt{321}}{\mathtt{\,\small\textbf+\,}}{\mathtt{204}} = {\mathtt{5\,310}}$$