Question 833113
Many started with variable, d dollars.


Store 1---{{{d-(2/5)d}}};
Store 2---{{{d-(3/5)(d-(2/5)d)}}};
Store 3---{{{highlight(d-(3/4)(d-(3/5)(d-(2/5)d))=6)}}}


Solve for d.  
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{{{d-(3/4)(d-(3/5)(d-(2/5)d))=6}}}
{{{d-(3/4)(d-(3/5)(5d/5-(2/5)d))=6}}}
{{{d-(3/4)(d-(3/5)(3d/5))=6}}}
{{{d-(3/4)(d-9d/25)=6}}}
{{{d-(3/4)(25d/25-9d/25)=6}}}
{{{d-(3/4)(16d/25)=6}}}
{{{d-48d/100=6}}}
{{{(100d-48d)/100=6}}}
{{{52d/100=6}}}
{{{d=6(100/52)}}}
{{{d=6(25/13)=150/13}}}
{{{highlight(d=11.54)}}}