Select three balls and put them into the circles, total sum must be 30?

The answer to select 3 balls and put into the circles is: 11 + 13 + 6 I know you people are wondering on how this number 6 has come. But let me tell you that the riddle says you need to put the balls to make it 30. It never said you need to put the numbers. So you just need to turn the ball which has written 9 and make it 6 and you get it.