How much more is the result of 15*20 than the result of 15*19
15*20的结果比15*19的结果多多少
<gadget id="calculator">15 * 20</gadget>
<output>300</output>

<gadget id="calculator">15 * 19</gadget>
<output>285</output>

<gadget id="calculator">300 - 285</gadget>
<output>15</output>

<result>15</result>