The ratio of the number A to the number B is 2:3, the number B minus the number A is 7.5, what is the number A
甲数和乙数的比是2：3，乙数减甲数得7.5，甲数是多少
<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">7.5 / 1</gadget>
<output>7.5</output>

<gadget id="calculator">7.5 * 2</gadget>
<output>15</output>

<result>15</result>