Hello,
if A.P means arithmetic progression then
let's say a the first term and r the common difference.
[tex]\left\{\begin{array}{ccc}(a)+(a+r)+(a+2r)+...+(a+5r)&=&72\\a+r&=&7*(a+4r)\end{array}\right.\\\\\\\left\{\begin{array}{ccc}6a+15r&=&72\\6a+27r&=&0\end{array}\right.\\\\\\\left\{\begin{array}{ccc}a&=&\dfrac{-9}{2}*r\\-9r+5r&=&24\end{array}\right.\\\\\\\left\{\begin{array}{ccc}r&=&-6\\a&=&27\end{array}\right.\\\\[/tex]
