The three classes of the sixth grade planted 200 trees in total. Class A planted 30% of the total. The ratio of trees planted by Class B to Class C was 4:3. How many more trees were planted by Class B than Class C?
六年级三个班共植树200棵，甲班植了总数的30%，乙班与丙班植树棵树之比是4：3，乙班比丙班多植多少棵树？
<gadget id="calculator">30 / 100</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">200 * (7/10)</gadget>
<output>140</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(4/7) - (3/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">140 * (1/7)</gadget>
<output>20</output>

<result>20</result>