Class 51 has 55 science books and some story books, and the number of science books is 15 fewer than twice the number of story books. How many story books does Class 51 have?
五一班有55本科技书和一些故事书，科技书的本数比故事书的2倍还少15本．五一班有故事书多少本？
<gadget id="calculator">15 + 55</gadget>
<output>70</output>

<gadget id="calculator">70 / 2</gadget>
<output>35</output>

<result>35</result>