Two 5-meter-long boards are nailed together to form a 8-meter-long board. How many meters is the overlapping part nailed together in the middle?
有两块5米长的木板钉在一起，成了一块长8米的长木板，中间钉在一起重叠的部分有多少米．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 8</gadget>
<output>2</output>

<result>2</result>