Since the country implemented the policy of home appliances going to the countryside to subsidize consumption, Limin Home Appliances Store has sent 210 color TVs to the countryside a month, 21 sets more than three times that of air conditioners. How many air conditioners does this home appliance store sell in a month? (solution with equation)
自从国家实行家电下乡补贴消费的政策起，利民家电商场一个月送了210台彩电下乡，比空调机的3倍还多21台．这个家电商场一个月销售下乡空调多少台？(用方程解答)
<gadget id="calculator">210 - 21</gadget>
<output>189</output>

<gadget id="calculator">189 / 3</gadget>
<output>63</output>

<result>63</result>