Total no. of possible outcomes = 20 {5 red, 8 white & 7 black}
(i) E ⟶ event of drawing red or white ball
No. of favourable outcomes = 13 {5 red, 8 white}
Probability, P(E) = (No.of favorable outcomes)/(Total no.of possible outcomes)
P(E) = 13/20
(ii) Let E ⟶ be event of getting black ball
No. of favourable outcomes = 13 {5 red, 8 white}
P(E) = 7/20
(Bar E)⟶ event of not getting black ball
P(Bar E) = 1 – P(E)
=1−7/20 = 13/20
(iii) Let E ⟶ be event of getting neither white nor black ball
No. of favourable outcomes = 20 – 8 – 7 = 5 {total balls – no. of white balls – no. of black balls}
P(E) = 5/20 = 1/4