Некоторые видные учёные-лингвисты утверждают, что местоимения не составляют самостоятельной части речи. Почему?

Пожалуйста, объясните своё решение!

Буду благодарна

Замените формы глаголов Indefinite Passive формами глаголов Indefinite Active: 1. The examinations were seldom passed by him well. 2. This text is usually translated by the students with the help of the teacher. 3. That book was read by my friends with great interest. 4. My sister will be waited by her friend after classes next Monday. 5. New copybooks were bought by her yesterday 6. Secondary school will be finished by him in a year. 7. We are often met by him near the school. 8. Museums and exhibitions are often visited by our family. 9. Saturdays and Sandays are never spent are often visited by our family. 10. The library was rerely visited by this pupil last year.

Пожалуйста,помогите решить,срочно.

а)4x(в квадрате)+8x

б)3m-6n+mn-2n(в квадрате)

в)9а(в квадрате)-16

г)y(в кубе)+18у(в квадрате)+81у

вВ равносторонний треугольник со стороной 8 см вписана окружность.Чему равен радиус окружности?