question_answer

Following are the marks obtained (Out of 50) by the students in a class.

Marks	Numbers 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 \[\frac{5}{7},\] then the value of x is

A)  13                               

B)  18

C)  6                                

D)  26

E)  None of these