Điền số thích hợp vào ô trống

a) \[\begin{array}{l} \times \begin{array}{*{20}{c}}{\,\,15}\\{\underline {\,\,\,24\,\,} }\end{array}\\\,\,\,........\\\,\,\,\underline {........} \\\,\,\,........\end{array}\]

b) \[\begin{array}{l} \times \begin{array}{*{20}{c}}{\,\,\,\,\,57}\\{\underline {\,\,\,\,13} }\end{array}\\\,\,\,........\\\,\,\,\underline {........} \\\,\,\,........\end{array}\]