Question

the probablity of guessing the correct answer to a certain question is X upon 3 if problem of not guessing the correct answer is 3 X upon 2 then find the value of x

Answer 1

x/3 + 3x/2 = 1
Take the LCM and solve the value of x.
We took RHS as 1 because the total sum of probabilities is 1

Answer 2

probability of guessing correct answer + probability of not guessing the correct answer = 1 
x/3  +3x/2  = 1 
2x+9x = 6
11x = 6 
x = 6/11