John cuts his grass to 2 inches.  It grows .5 inches per month.  When it gets to 4 inches he cuts it back down to 2 inches.  It cost $100 to get his grass cut.  How much does he pay per year?
He cuts his grass 4-2=
<gadget id="calculator">4-2</gadget>
<output>2</output>
2 inches.
So he gets it cut every 2/.5=
<gadget id="calculator">2/.5</gadget>
<output>4</output>
4 months.
That means he gets it cut 12/4=
<gadget id="calculator">12/4</gadget>
<output>3</output>
3 times a year.
So he pays 100*3=$
<gadget id="calculator">100*3</gadget>
<output>300</output>
300 per year.

<result>300</result>