A certain school held a model airplane competition, with a number of first, second, and third prizes. Those who won the first and second prizes accounted for 7/10 of the total number of winners, and those who won the second and third prizes accounted for 7/10 of the total number of winners. (9/10), those who won the second prize accounted for ((())/(())) of the total number of winners.
某校举办一次航模比赛，设一、二、三等奖若干名，竞赛结果获一、二等奖的占获奖总人数的(7/10)，获二、三等奖的占获奖总人数的(9/10)，获二等奖的占获奖总人数的((())/(()))．
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(9/10) - 1</gadget>
<output>-1/10 = around -0.1</output>

<gadget id="calculator">(7/10) + (-1/10)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>