Ответ:

  1. а) \(\frac{4b+12}{3(b+3)}=\frac{4(b+3)}{3(b+3)}=\frac{4}{3}\).
  2. б) \(\frac{3x-2x}{12(x-1)}=\frac{x}{12(x-1)}\).
  3. в) \(\frac{b+a}{ab(a+b)}=\frac{1}{ab}\).
  4. г) \(\frac{3x^2-3y^2}{xy(x+y)}=\frac{3(x-y)(x+y)}{xy(x+y)}=\frac{3(x-y)}{xy}\).