Question 1155016
If that's all the information, then it is
a simple interest problem. For simple 
interest:
{{{ I = P*r*t }}}
where:
{{{ I }}} = interest earned
{{{ P }}} = amount invested
{{{ r }}} = interest rate
{{{ t }}} time in years of investment
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This problem sounds like it is for 1 year, so
{{{ I = P*r*t }}}
{{{ 600 = P*.03*1 }}}
{{{ P = 600 / .03 }}}
{{{ P = 20000 }}}
$20,000 was her amount invested