The store has 200 pens and pencils. When the same number of pens and pencils are sold, there are 30 pens left and 70 pencils left. How many original pens are there in the store?
商店有钢笔和铅笔共200支．当卖出相同支数的钢笔和铅笔时，钢笔还剩下30支，铅笔还剩下70支．商店原有钢笔多少支．
<gadget id="calculator">70 - 30</gadget>
<output>40</output>

<gadget id="calculator">200 - 40</gadget>
<output>160</output>

<gadget id="calculator">160 / 2</gadget>
<output>80</output>

<result>80</result>