There are two boxes of thumbtacks, box A has 80 pieces, and box B has 58 pieces. How many thumbtacks are taken from box A and put into box B so that the number of thumbtacks in the two boxes are equal?
有两盒图钉，甲盒有80只，乙盒有58只，从甲盒中拿出多少放入乙盒，才能使两盒中的图钉相等？
<gadget id="calculator">80 + 58</gadget>
<output>138</output>

<gadget id="calculator">138 / 2</gadget>
<output>69</output>

<gadget id="calculator">80 - 69</gadget>
<output>11</output>

<result>11</result>