Your brother's a doctor. (Frase negativa)
Your brother isn't a doctor.
Your brother is a not doctor.
Teachers are on holiday in August. (Frase interrogativa)
Teachers are on holiday in August?
Are teachers on holiday in August?
I'm late for class. (Frase interrogativa)
am i late for class?
i late for class?
She's married. (Frase negativa)
Isn't she married.
She isn't married.
They're my friends. (Frase negativa)
They aren't my friends
Not are they my friends