Question 1129096
m marbles to start with


{{{m-m/3-(1/2)(m-m/3)=12}}}

{{{m-m/3-(m/2-m/6)=12}}}

{{{m-m/3-m/2+m/6=12}}}

multiply both sides by 6.

{{{6m-2m-3m+m=72}}}

{{{2m=72}}}

{{{highlight(m=36)}}}