Number between 6/11 and 67/99

a. 11/18
b. 69/99
c. 24/33
d. 26/55

Simple, find what 6/11 and 67/99 is in decimal form

6/11=0.545454545 (repeating)
and
67/99=0.67676767 (repeating)
then do the same with your answer choices:

11/18=0.61111111 (repeating)

69/99=0.696969697  (too high)

24/33=0.727272727 (repeating)  (too high)

26/55=0.472727273   (too low)

Then, from here it's simple to see what the answer is, 11/18, is your answer.