Question 1098457
Let {{{ x }}} = the quarts of pure alcohol 
in the 4 quarts she added
{{{ 4 - x }}} = the amount of water 
in the 4 quarts she added
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I can say:
{{{ x / ( 4 + 1 ) = .36 }}}
{{{ x = .36*5 }}}
{{{ x = 1.8 }}}
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{{{ x/4 = 1.8/4 }}}
{{{ 1.8/4 = .45 }}}
The concentration of the 4 quarts added is 45%