Bonjour,
[tex] \frac{19}{ \frac{18}{ \frac{25}{27} - \frac{7}{3} } } [/tex]
[tex] = \frac{19}{ \frac{18}{ \frac{ - 38}{27} } } [/tex]
[tex] = \frac{19}{18} \times \frac{27}{ - 38} [/tex]
[tex] = - \frac{513}{684} [/tex]
[tex] = - \frac{171}{228} [/tex]
[tex] = - \frac{57}{76} [/tex]