Question 1086032
{{{a[3]=a[1]+(3-1)d=a[1]+2d=3}}}
{{{a[6]=a[1]+(6-1)d=a[1]+5d=1/9}}}
Subtracting,
{{{a[6]-a[3]=a[1]+5d-a[1]-2d=3d=1/9-3}}}
{{{3d=1/9-27/9}}}
{{{3d=-26/9}}}
{{{d=-26/27}}}
So then,
{{{a[1]+5(-26/27)=1/9}}}
{{{a[1]-130/27=3/27}}}
{{{a[1]=133/27}}}