Nancy can hula hoop for 10 minutes.  Casey can hula hoop 3 minutes less than Nancy.  Morgan can hula hoop three times as long as Casey.  How long can Morgan hula hoop?
Casey can hula hoop 3 minutes less than Nancy so she can hula hoop for 10-3 = 
<gadget id="calculator">10-3</gadget>
<output>7</output>
7 minutes.
Morgan can hula hoop three times as long as Casey, who can hula hoop for 7 minutes, so she can hula hoop for 3*7 = 
<gadget id="calculator">3*7</gadget>
<output>21</output>
21 minutes.

<result>21</result>