Question 1156881
Let {{{ x }}} = amount that Michael at beginning 
{{{ 3x }}} = amount Karen had at beginning
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{{{ 3x - 9 }}} = amount Karen has later
{{{ x + 5 }}} = amount Michael has later
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given:
{{{ 3x - 9 = x + 5 }}}
{{{ 2x = 14 }}}
{{{ x = 7 }}}
and
{{{ 3x = 21 }}}
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Karen had $21 at first
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check:
{{{ 3x - 9 = x + 5 }}}
{{{ 21 - 9 = 7 + 5 }}}
{{{ 12 = 12 }}}
OK