Mel is three years younger than Katherine.  When Katherine is two dozen years old, how old will Mel be in years?
When Katherine is 2 dozen years old, she will be 2*12=
<gadget id="calculator">2*12</gadget>
<output>24</output>
24 years old.
If Mel is three years younger than Katherine, then when Katherine is 24 years old, Mel will be 24-3=
<gadget id="calculator">24-3</gadget>
<output>21</output>
21 years old.

<result>21</result>