Hi, thanks Alan again!
$(63)=20$waystochoose3islands.Foreachofthesechoices,thereisaprobabilityof$(14)3(23)3$thatthechosenislandshavetreasureandtheremainingoneshaveneithertreasurenortraps.Therefore,theprobabilitythatthepirateencountersexactly3islandswithtreasureandnonewithtrapsis$20(14)3(23)3=554$.H