The last time Bob cut his hair he cut it to 6 inches.  His hair is now 36 inches long.  If hair grows at a rate of .5 inches per month how many years did it take him to grow out his hair?
His hair grew 36 inches - 6 inches = 
<gadget id="calculator">36-6</gadget>
<output>30</output>
30 inches.
Hair grows at a rate of 12 months/year * 0.5 inches/month =
<gadget id="calculator">12*0.5</gadget>
<output>6</output>
6 inches/year.
It took him 30 inches / 6 inches/year = 
<gadget id="calculator">30/6</gadget>
<output>5</output>
5 years to grow his hair out.

<result>5</result>