Question 1160735
The principal is {{{COST/PERSONS=PRICE}}}


n, unknown number of friends in the group


I assume here that EACH paying friend had to pay an extra  R40.
<pre>
                     PRICE          PERSONS         COST

ALL FRIENDS          960/n           n              960

TWO NOT PAY         960/(n-2)        n-2            960

DIFFERENCE           40
</pre>
{{{highlight_green(960/(n-2)-960/n=40)}}}--------simplify and solve this for n.