A store originally had 630 black and white and color TV sets, of which black and white TVs accounted for (1/5), and some black and white TV sets were shipped in later. At this time, black and white TV sets accounted for (3/10) of the total number of the two types of TV sets. Ask: How many black and white TV sets are shipped in?
某商店原有黑白、彩色电视机共630台，其中黑白电视机占(1/5)，后来又运进一些黑白电视机．这时黑白电视机占两种电视机总台数的(3/10)，问：又运进黑白电视机多少台？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3 / 10</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">(4/5) / (7/10)</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">630 * (8/7)</gadget>
<output>720</output>

<gadget id="calculator">720 - 630</gadget>
<output>90</output>

<result>90</result>