If a certain color TV set is sold at a discount, if it is sold at a 10% discount, it can still make a profit of 210 yuan. If it is sold at a 20% discount, it will lose 120 yuan. So how much is the purchase price of this TV set?
某种彩色电视机要让利销售，如果按销售价打九折出售，还可盈利210元，如果按八折出售就要亏损120元，那么这种电视机的进价是多少元？
<gadget id="calculator">210 + 120</gadget>
<output>330</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/10) - (4/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">330 / (1/10)</gadget>
<output>3_300</output>

<gadget id="calculator">3_300 * (4/5)</gadget>
<output>2_640</output>

<gadget id="calculator">2_640 + 120</gadget>
<output>2_760</output>

<result>2_760</result>