Question 753616
{{{a[n]=a[1]+(n-1)*d}}}
Since {{{d=-2/3}}} and {{{a[4]=18}}},
{{{18=a[1]+(4-1)*(-2/3)}}} --> {{{18=a[1]+3*(-2/3)}}} --> {{{18=a[1]-2}}} --> {{{18+2=a[1]}}} --> {{{a[1]=20}}}
So
{{{a[23]=a[1]+(23-1)*d}}} --> {{{a[23]=20+22*(-2/3)}}} --> {{{a[23]=60/3-44/3)}}} --> {{{highlight(a[23]=16/3))}}} or {{{highlight(a[23]=5&1/3))}}}