Сократите дробь: a) $$rac{24xy^7}{32x^3y^4}$$; б) $$rac{7a^2+21a}{14a}$$; в) $$rac{b^2-64}{5b-40}$$

a) $$rac{24xy^7}{32x^3y^4} = \frac{3y^3}{4x^2}$$ б) $$rac{7a^2+21a}{14a} = \frac{7a(a+3)}{14a} = \frac{a+3}{2}$$ в) $$rac{b^2-64}{5b-40} = \frac{(b-8)(b+8)}{5(b-8)} = \frac{b+8}{5}$$