In order to develop students’ sports activities better, a certain elementary school added 30 balls of three kinds, which cost 1268 yuan. It is known that each basketball is 51 yuan, each football is 38 yuan, and each volleyball is 42 yuan. The number is twice the number of basketballs, how many basketballs are there?
某小学为了把学生的体育活动开展得更好，增添了三种球共30个，用去1268元，已知篮球每个51元，足球每个38元，排球每个42元，足球的个数是篮球个数的2倍，篮球有多少个？
<gadget id="calculator">42 * 30</gadget>
<output>1_260</output>

<gadget id="calculator">1_268 - 1_260</gadget>
<output>8</output>

<gadget id="calculator">38 * 2</gadget>
<output>76</output>

<gadget id="calculator">42 * 2</gadget>
<output>84</output>

<gadget id="calculator">76 - 42 - 84</gadget>
<output>-50</output>

<gadget id="calculator">51 + (-50)</gadget>
<output>1</output>

<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<result>8</result>