Question 1137213
<br>
Let the number of members be x, and the amount they each contribute be y.  Then<br>
{{{(x+3)(y-10) = xy}}}
{{{xy-10x+3y-30 = xy}}}
{{{-10x+3y = 30}}}  (1)<br>
and<br>
{{{(x-2)(y+10) = xy}}}
{{{xy+10x-2y-20 = xy}}}
{{{10x-2y = 20}}}  (2)<br>
Adding (1) and (2) eliminates x and gives us the value of y:
{{{y = 50}}}<br>
Then substituting y=50 in either (1) or (2) gives us x=12.<br>
ANSWER:  The number of members in the club is x = 12.<br>
CHECK:
xy = 12(50) = 600
(x+3)(y-10) = 15(40) = 600
(x-2)(x+10) = 10(60) = 600