Question 1185956
Box began with 13 biscuits.

Roy at 4 biscuits.


p, for how many bisquits starting in the box,


After Roy,
{{{p/3-1/3}}}


After Sam,
.
.
{{{p/9-4/9}}}


After Tom,
.
.
{{{(1/3)(p/9-4/9)-1/3=0}}}
.

.
{{{p=13}}}