Xiaodong bought 4 fountain pens and 11 ballpoint pens with his own pocket money, leaving 3/10 of the total pocket money. If Xiaodong spends all his pocket money to buy pens, he can buy a total of 12 pens. So, all the pocket money is used to buy ballpoint pens, how many can I buy in total?
小东用自己的零花钱，买了4枝钢笔和11枝圆珠笔，后还剩下零花钱总数的(3/10)．如果，小东把零花钱都拿去买钢笔一共可以买12枝．那么，这些零花钱都拿去买圆珠笔，一共可以买几枝？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 4</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (1/3) - (3/10)</gadget>
<output>11/30 = around 0.366667</output>

<gadget id="calculator">(11/30) / 11</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>