The possibility of pulling a yellow ball pulled from a basket of 5 white and 5 blue balls is .
7. There are 18 balls in a jar. You take out 3 blue balls without putting them back inside, and now the probability of pulling out a blue ball is 1/5. How many blue balls were there in the beginning?
The probability of drawing a blue ball from a bag that contains 3 white balls, 8 blue balls and 5 red balls is