The school bought 4 chairs and 5 tables for a total of 420 yuan, and the price of each table is twice that of each chair. How much is each chair?
学校买了4把椅子和5张桌子共花420元，每张桌子的价钱是每把椅子的2倍．每把椅子多少元？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">4 + 10</gadget>
<output>14</output>

<gadget id="calculator">420 / 14</gadget>
<output>30</output>

<result>30</result>