<PRE><B>Question 1029525</B>
{{{A[4]=A[1]+(4-1)d=A[0]+3d=24}}}
{{{A[7]=A[1]+(7-1)d=A[0]+6d=64/9}}}
Subtracting,
{{{A[1]+6d-A{1]-3d=64/9-24}}}
{{{3d=-152/9}}}
{{{d=-152/27}}}
So then,
{{{A[1]+3(-152/27)=24}}}
{{{A[1]-152/9=216/9}}}
{{{A[1]=368/9}}}
.
.
{{{A[n]=368/9+(n-1)(-152/27)}}}
.
.
{{{S[n]=(n/2)(A[1]+A[n])}}}
{{{S[n]= (n/2)(368/9+368/9+(n-1)(-152/27)) }}}
{{{S[n]=(4/27)n(295-19n)}}}</PRE>