Question 941828
{{{N-1/N=21/10}}}
Multiply both sides by {{{10N}}}
{{{10N^2-10=21N}}}
{{{10N^2-21N-10=0}}}
{{{(2N-5)(5N+2)=0}}}
Two solutions:
{{{2N-5=0}}}
{{{2N=5}}}
{{{N=5/2}}}
and
{{{5N+2=0}}}
{{{5N=-2}}}
{{{N=-2/5}}}