rational number are those nubers which can be expressed in the form of P/Q where P and Q are integers and Q not equal to zero.
so in between 0 and -3/4
just find the average of the above numbers
we have
(1/2)( 0+ (-3/4))= -3/8
For another number , (1/2) (0+ -3/8)= -3/16
and (1/2)(-3/8 + -3/4 )= -9/16
so thre ratonal numbers are (-3/8) (-3/16) and (-9/16)
There are other number also , but i have given a way to find rational number betwwen two numbers.
Like if satisfied