Question 877374
The profit percentage would be:
( selling price - cost of TV ) / ( cost of TV )
Let {{{ x }}} = cost of  TV 
She bought it for {{{ x - .2x = .8x }}}
She sold it for {{{ x + .2x = 1.2x }}}
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profit % = {{{ ( 1.2x - .8x ) / .8x }}}
Divide top and bottom by {{{ x }}}
{{{ ( 1.2 - .8 ) / .8 = .4/.8 }}}
{{{ .4/.8 = .5 }}}
profit % = 50%