"Seven Star Electric City" held a store celebration, and all electrical appliances will be reduced by 15%. Xiaoming's family bought a color TV with "trade-in". Xiaoming's old color TV is equivalent to 10% of the price of the discounted color TV. If the original price of this new color TV is 4,200 yuan, how much did Xiao Ming's family spend on this color TV?
"七星电器城"举行店庆，所有电器一律降价15%．小明家"以旧换新"购买了一台彩电．小明家的旧彩电折合打折后彩电价格的10%．如果这台新彩电的原价是4200元，那么小明家买这台彩电花了多少元？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">4_200 * (17/20) * (9/10)</gadget>
<output>3_213</output>

<result>3_213</result>