The original price of a small color TV is 4,200 yuan, but the current price is 100 yuan less than the original price (6/7). How much is the current price?
一种小彩电原价4200元，现价比原价的(6/7)还少100元．现价多少元？
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">4_200 * (6/7)</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 - 100</gadget>
<output>3_500</output>

<result>3_500</result>