Calculation (7/15)+(2/7)+□, how much to choose in □ can make the calculation simple.
计算(7/15)+(2/7)+□，□里选多少可以使算式简便．
<gadget id="calculator">8 / 15</gadget>
<output>8/15 = around 0.533333</output>

<result>8/15 = around 0.533333</result>