Answer
$-\frac{9}{10}$
Work Step by Step
To write the fraction in its simplest form, find the greatest common factor of the numerator and denominator.
$ -\frac{72}{80}= -\frac{8\times 9}{8\times 10}$
Cancel out the greatest common factor
$-\frac{8\times 9}{8\times 10}= -\frac{9}{10}$
