Dalin did 15 more math problems than Xiao Lin, Xiao Ming did 6 more math problems than Xiao Lin, how many more math problems did Dalin do than Xiao Ming?
大林比小林多做15道口算题，小明比小林多做6道口算题，大林比小明多做几道口算题？
<gadget id="calculator">15 + 1</gadget>
<output>16</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">16 - 7</gadget>
<output>9</output>

<result>9</result>