question_answer

Following are the marks obtained (Out of 50) by the students in a class.
Marks	No. of Students
10-20	8
20-30	X
30-40	9
40-50	6
One student from the class is selected at random. If the, probability that his marks is 20 or more but less than 40, is \[\frac{\mathbf{5}}{\mathbf{7}}\], then find the  value of x.

A) 13                                                                    

B) 18          

C) 6                                                                     

D) 26

E) None of these