Among the 54 students in Class 1, the survey found that 50% of the students can swim, (1/3) of the students can do gymnastics, 15 can neither swim nor gymnastics, how many can both swim and gymnastics.
六一班54位同学中，调查中发现50%的同学会游泳，(1/3)的同学会体操，游泳和体操都不会的有15人，既会游泳又会体操的有多少人．
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">54 * (1/2)</gadget>
<output>27</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">54 * (1/3)</gadget>
<output>18</output>

<gadget id="calculator">15 - 54</gadget>
<output>-39</output>

<gadget id="calculator">27 + 18 + (-39)</gadget>
<output>6</output>

<result>6</result>