A stationery store buys several ballpoint pens at a price of 7 yuan each. If they sell them at 9 yuan each, the amount they get from selling (1/3) another 20 pens is exactly equal to the amount they bought. Find out how to buy ballpoint pens How many sticks?
某文具店买入圆珠笔若干支，每支价7元，如果按每支9元卖出，卖去(1/3)又20支所得的金额恰好等于全部买入的金额，求原来买入圆珠笔多少支？
<gadget id="calculator">20 * 9</gadget>
<output>180</output>

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

<gadget id="calculator">(1/3) * 9</gadget>
<output>3</output>

<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">180 / 4</gadget>
<output>45</output>

<result>45</result>