Difficult!

Select the right operation


../sonsmp3/one.mp3

../sonsmp3/two.mp3

../sonsmp3/three.mp3

../sonsmp3/four.mp3

../sonsmp3/five.mp3

../sonsmp3/six.mp3

../sonsmp3/seven.mp3

../sonsmp3/eight.mp3

../sonsmp3/nine.mp3

../sonsmp3/ten.mp3