The school bought 3 tables and 4 chairs and spent a total of 420 yuan. It is known that each table is 80 yuan, how much is each chair?
学校买来3张桌子和4把椅子，一共花去420元．已知每张桌子80元，每张椅子多少元？
<gadget id="calculator">3 * 80</gadget>
<output>240</output>

<gadget id="calculator">420 - 240</gadget>
<output>180</output>

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

<result>45</result>