Gwen had 18 math problems and 11 science problems for homework. If she finished 24 of the problems at school, how many problems did she have to do for homework?
<gadget id="calculator">18 + 11</gadget>
<output>29</output>

<gadget id="calculator">29 - 24</gadget>
<output>5</output>

<result>5</result>