Đặt tính rồi tính: 420 646 + 310 528

\[\begin{array}{l} + \begin{array}{*{20}{c}}{420\,\,646}\\{\underline {310\,\,528} }\end{array}\\\,\,\,\,\,731\,\,174\end{array}\]

\[\begin{array}{l} - \begin{array}{*{20}{c}}{568\,\,235}\\{\underline {346\,\,319} }\end{array}\\\,\,\,\,221\,\,916\end{array}\]