#### Answer

$\dfrac{\dfrac{m}{n}-1}{\dfrac{m}{n}+1}=\dfrac{m-n}{m+n}$

#### Work Step by Step

$\dfrac{\dfrac{m}{n}-1}{\dfrac{m}{n}+1}$
Evaluate the substraction indicated in the numerator and the sum indicated in the denominator:
$\dfrac{\dfrac{m}{n}-1}{\dfrac{m}{n}+1}=\dfrac{\dfrac{m-n}{n}}{\dfrac{m+n}{n}}=...$
Evaluate the division and simplify if possible:
$...=\dfrac{m-n}{n}\div\dfrac{m+n}{n}=\dfrac{(m-n)(n)}{(m+n)(n)}=\dfrac{m-n}{m+n}$