A worksheet had 4 problems on it. If a teacher had 9 worksheets to grade and had already graded 5 of them, how many more problems does she have to grade?
<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<result>16</result>