John buys cans of soup for buy 1 get one free.  He gets 30 cans with a normal price of $0.60.  How much does he pay?
He pays for 30/2=
<gadget id="calculator">30/2</gadget>
<output>15</output>
15 cans.
So he spends 15*.6=$
<gadget id="calculator">15*.6</gadget>
<output>9</output>
9.

<result>9</result>