John and Sam were hungry so they ordered an extra-large pizza that was pre-sliced into 12 pieces.  John ate 3 slices while Sam ate twice the amount that John ate.  How many slices of pizza were left?
Sam had twice the amount of John so Sam ate 3*2 = 
<gadget id="calculator">3*2</gadget>
<output>6</output>
6 slices.
Together, they ate 3+6 = 
<gadget id="calculator">3+6</gadget>
<output>9</output>
9 slices
1 pizza has 12 slices. 9 slices were eaten so 12-9= 
<gadget id="calculator">12-9</gadget>
<output>3</output>
3 slices left.

<result>3</result>