The probability of getting a correct answer to question is $\frac{x}{12}$. If the probability of not getting the correct answer is $\frac{2}{3}$, then what is the value of x ?

4

Let E denote the event of guessing a correct question and E bar denote the event of not guessing a correct question .

Given probability of guessing a certain question is P(E) = (x/12)

Hence probability of not guessing answer isP(E') = (2/3)

P(E) + P(E') = 1

x /12 + 2 / 3 = 1

x /12 = 1 / 3

∴x = 4