The school cafeteria ordered 42 red apples and 7 green apples for students lunches. But, if only 9 students wanted fruit, how many extra did the cafeteria end up with?
<gadget id="calculator">42 + 7</gadget>
<output>49</output>

<gadget id="calculator">49 - 9</gadget>
<output>40</output>

<result>40</result>