The ratio of number A to number B is 2:3, and the ratio of number B to number C is 6:5. The average of these three numbers is 30. Find the number A.
甲数和乙数的比是2：3，乙数和丙数的比是6：5，这三个数的平均数是30，求甲数．
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">4 + 6 + 5</gadget>
<output>15</output>

<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">90 * (4/15)</gadget>
<output>24</output>

<result>24</result>