Riven Riven 20-04-2024 Mathematics College Timothy stated that the sum of [tex]0.9 + \left(-\frac{9}{10}\right)[/tex] was [tex]\frac{18}{20}[/tex]. What mistake(s) did Timothy make? What is the correct sum of [tex]0.9 + \left(-\frac{9}{10}\right)[/tex]?