Let p(E) be the probability of getting success.
let p(notE) be the probability of getting failure.
p(E) - p(notE) = 3/13 ⇒1
we know that
p(E)+ p(notE) = 1
substitute p(E)in EQ 1
8/13-p(notE) = 3/13
⇒probability of getting success is 8/13
⇒probability of getting failure is 5/13