Answer:
First, you get both of them with same denominator:
3/7 and 2/3 => 9/21 and 14/21, however, there are only 4 rational numbers between 9/21 and 14/21.
The solution is that you can raise the denominator 2 times:
9/21 and 14/21 => 18/42 and 28/42
Now you can select : 19/42, 20/42, 21/42, 22/42, 23/42. They are a group of 5 rational numbers you are looking for.
