Xiao Zhang brought 35 yuan, and Li Qiang brought 15 yuan to buy a leather bag. The two people's money together just bought two identical bags. How much should Li Qiang pay Xiao Zhang after buying them back?
小张带35元，李强带了15元去买皮包，两人的钱合起来刚好购买两个相同的皮包，买回来后李强应还小张多少钱？
<gadget id="calculator">35 + 15</gadget>
<output>50</output>

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">25 - 15</gadget>
<output>10</output>

<result>10</result>