Question

Find a rational. number between 2/3
and 3/4

Answer 1

multiply the denominator of 2/3 by the rational no. 3/4 
so you will get 8/12 and 9/12
now you can see the denominator of both the no. becomes same but there is no no. between 8 and 9
so you can again multiply both the no. by 10 

so you'll get 80/120 and 90/120 

now you can see there are three no. between 80/120 and 90/120

like 81/120  ,  82/120  ,  83/120 .......and many more

hope this will help you
cheers....