Dad spent 279 yuan to buy a Walkman with a 10% discount. How much is it cheaper than the original price?
爸爸花279元买了一个打九折的随身听，比原价便宜了多少钱？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">279 / (9/10)</gadget>
<output>310</output>

<gadget id="calculator">310 - 279</gadget>
<output>31</output>

<result>31</result>