A total of 210 pencils of type A and type B are bought. Each type A pencil is worth 3 cents, and each type B pencil is worth 4 cents. The money spent on the two types of pencils is the same.
买甲、乙两种铅笔共210支，甲种铅笔每支价值3分，乙种铅笔每支价值4分，两种铅笔用去的钱相同，甲种铅笔买了多少支．
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">210 * (4/7)</gadget>
<output>120</output>

<result>120</result>