First, convert 0.12 and 0.13 into their rational form, i.e., the p/q form.
0.12 = 12/100 ; 0.13 = 13/100
Now, multiply the numerator and the denominator of both the numbers by 10. (You can multiply them by any number but 10 will do.)
(12*10)/(100*10) = 120/1000 ; (13*10)/(100*10) = 130/1000
Now, pick any two numbers between 120/1000 and 130/1000 as your answer.
You can easily find nine rational numbers between these two numbers
= 121/1000=(0.121), 122/1000=(0.122), 123/1000=(0.123), 124/1000=(0.124), 125/1000=(0.125)