Question 1088697
Let {{{ c }}} = his cost for the shoes
{{{ c - .2c = 2800 }}}
{{{ .8c = 2800 }}}
{{{ c = 3500 }}
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His loss was 
{{{ .2c = .2*3500 }}}
{{{ .2c = 700 }}}
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As % of his selling price:
{{{ ( 700/2800 )*100 = 25 }}}
25%