John's grill messes up and burns half his steak.  He eats 80% of what isn't burned.  If the steak was originally 30 ounces how much steak did he eat?
There were 30*.5=
<gadget id="calculator">30*.5</gadget>
<output>15</output>
15 ounces of unburnt steak.
So he ate 15*.8=
<gadget id="calculator">15*.8</gadget>
<output>12</output>
12 ounces of steak.

<result>12</result>