Let the number of blue balls be X
So total number of balls = 5 + X
P(probability of drawing a red ball from the bag) = 5/(5 + X)
P(probability of drawing a blue ball from the bag) = 4 5/(5 + X)
ATQ ,
5X +X2 = 100+20X
X2 - 15X+ -100 = 0
(x-20)(x+5) =0
So X ≠ -5
Therefore No. Of blue balls = 20