The ratio of number A to number B is 7:5. If the sum of these two numbers is 1.8, what is the difference between them?
甲数与乙数的比是7：5，如果这两个数的和是1.8，那么它们的差是多少．
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">1.8 / 12</gadget>
<output>0.15</output>

<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">0.15 * 2</gadget>
<output>0.3</output>

<result>0.3</result>