The original price of a shirt is 210 yuan, how much is the price after 30% off.
一件衬衫的原价是210元，打七折后的售价是多少元．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">210 * (7/10)</gadget>
<output>147</output>

<result>147</result>