The Young Pioneers organized 50 students to prepare for a picnic and required the students to bring their own food and cooking utensils, at least one of the two. 38 people prepared food, 15 people prepared cooking utensils, how many people prepared both?
少先队组织50名学生筹备野炊活动，要求学生自备食品和炊具，两样中每人至少准备一样．有38人准备了食品，有15人准备了炊具，两样都准备的有多少人？
<gadget id="calculator">15 - 50</gadget>
<output>-35</output>

<gadget id="calculator">38 + (-35)</gadget>
<output>3</output>

<result>3</result>