56 people solve two math problems at the same time, among them 45 people get the first problem right, 49 people get the second problem right, how many people get both problems right?
56人同时做两道数学题，其中做对第一题的有45人，做对第二题的有49人，两道题都做对的有多少人？
<gadget id="calculator">49 - 56</gadget>
<output>-7</output>

<gadget id="calculator">45 + (-7)</gadget>
<output>38</output>

<result>38</result>