Question 824909
The rate of DRAINING the tank is when all pipes are open, {{{-1/18-1/27+1/6=-1/(2*3*3)-1/(3*3*3)+1/(2*3)
-1*2*3/(54)-2/54+9/54=highlight(1/54)}}}, tanks per minute.


The tank at 2/3 full and having all three pipes open would be drained when m minutes pass:  {{{(1/54)*m=2/3}}}
{{{m=(2/3)(54/1)}}}
{{{m=18}}} minutes