The restaurant buys a total of 60 stools with three legs and four legs, and there are 200 legs in total. Then, how many stools with three legs should you buy?
饭店购买三条腿的凳子和四条腿的凳子共60个，共有腿200条，那么，买三条腿的凳子多少个．
<gadget id="calculator">60 * 4</gadget>
<output>240</output>

<gadget id="calculator">240 - 200</gadget>
<output>40</output>

<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">40 / 1</gadget>
<output>40</output>

<result>40</result>