Algebra Rule 7
Reversing a subtraction in both the numerator and the denominator of a fraction leaves the fraction's value unchanged
```{(a-b) \over (c-d)} = {(b-a) \over (d-c)}```
Description:
Reversing a subtraction gives the inverse result: ``5-3 = 2; 3-5 = -2``. In a fraction, if both the numerator and the denominator are inverted, the value of the fraction stays the same. So, if we reverse a subtraction in both the numerator and denominator, the value of the fraction is unchanged.
```{3-5 \over 2-1} = {-2 \over 1} = {5-3 \over 1-2} = {2 \over -1} = -2``` or ```{-3 \over -4} = 0.75 = {3 \over 4}```