The sum of (1/2) and (2/5) of a number is (2/15), what is this number?
一个数的(1/2)与它的(2/5)的和是(2/15)，这个数是多少？
<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) + (2/5)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(2/15) / (9/10)</gadget>
<output>4/27 = around 0.148148</output>

<result>4/27 = around 0.148148</result>