What fractions are in between -1/3 any -2/3

To find a fraction between two fractions, all we need to do is make the sum of the numerators be the new numerator, and the sum of the denominators be the new denominator.(x) So, for example, a fraction between 7/13 and 6/11 is (7 + 6)/(13+ 11) =13/24.(x)

7/13 = .5384615(x)

6/11 = .545454(x)

13/24 = .541666�

Given that a/b < c/d, why is it true that a/b < (a+c)/(b+d)< c/d?

ab will be equal to