When calculating (7/15)+(2/7)+□, if the simple method can be used, how much to fill in □
计算(7/15)+(2/7)+□时，若可以使用简便方法，则□里填多少
<gadget id="calculator">8 / 15</gadget>
<output>8/15 = around 0.533333</output>

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