Question 57956
The formula for the ith member of your series seems to be:
{{{Series[i]=10(i+1)+(i+3)}}}
The question is what value of i makes {{{Series[i]=200}}}?
{{{200=10(i+1)+(i+3)}}}
{{{200=10i+10+i+3}}}
{{{200=11i+13}}}
{{{11i=200-13}}}
{{{i=(200-13)/11}}}
{{{i=187/11}}}
{{{i=17}}}