C is (2/3) of the number of A, and (4/5) of the number of B, then the average of the two numbers of A and B is the number of C. (expressed in fractions)
丙是甲数的(2/3)，是乙数的(4/5)，那么甲、乙两数平均数是丙的多少．(用分数表示)
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(3/2) + (5/4)</gadget>
<output>11/4 = around 2.75</output>

<gadget id="calculator">(11/4) / 2</gadget>
<output>11/8 = around 1.375</output>

<result>11/8 = around 1.375</result>