What is the probability of drawing either a queen or a red card from a deck of $52$ cards?

If $P(A) = 0.4$,$P(B) = x$,$P(A \cup B) = 0.7$ and the events $A$ and $B$ are mutually exclusive,then $x = $

If the probability of a horse $A$ winning a race is $1/4$ and the probability of a horse $B$ winning the same race is $1/5$,then the probability that either of them will win the race is (in $/20$)

The odds against a certain event are $5: 2$ and the odds in favour of another independent event are $6: 5$. The probability that at least one of the events will happen,is

The probability that a student will succeed in the $IIT$ entrance test is $0.2$ and the probability that he will succeed in the Roorkee entrance test is $0.5$. If the probability that he will be successful at both places is $0.3$,then the probability that he does not succeed at either place is:

$A$,$B$,and $C$ are three events,one of which must and only one can happen. The odds in favor of $A$ are $4 : 6$,and the odds against $B$ are $7 : 3$. Thus,the odds against $C$ are: