Answer :
[tex]a-length\ one\ of\ the\ same\ sides\\\\a-9-length\ of\ third\ side\\\\a+a+a-9=63\ \ \ \ \ \ |add\ 9\\a+a+a=63+9\\3a=72\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |divide\ by\ 3\\a=24\\\\a-9=24-9=15\\\\The\ shortest\ side\ is\ 15.[/tex]