Question 160728
Let N be the number of members in the club now.
The per-person price now is,
{{{PPN=200000/N}}}
The per-person price when 5 more join is,
{{{PPF=200000/(N+5)}}}
You also know that,
{{{PPF=PPN-2000}}}
Substitute for your expression with N,
{{{PPF=PPN-2000}}}
{{{200000/(N+5)=200000/N-2000}}}
{{{200000N=200000(N+5)-2000N(N+5)}}}
{{{200N=200(N+5)-2N(N+5)}}}
{{{200N=200N+1000-2N^2-10N)}}}
{{{2N^2+10N-1000=0)}}}
{{{N^2+5N-500=0}}}
{{{(N+25)(N-20)=0)}}}
.
.
.
{{{N+25=0}}}
{{{N=-25}}} 
A negative answer doesn't make sense in our case.
{{{N-20=0}}}
{{{N=20}}}
There are 20 members currently.