An electronic watch is priced at 21 yuan each, which is 30% lower than the original price. How much is the original price?
一种电子表，每只售价21元，比原来降低了30%，原价每只多少元？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">21 / (7/10)</gadget>
<output>30</output>

<result>30</result>