c)
\frac{3x-6}{x-1}+ \frac{6x-1}{2x+2}=\frac{(3x-6)(2x+2)+(6x-1)(x-1)}{(x-1)(2x+2)}=
=\frac{6x^2+6x-12x-12+6x^2-6x-x+1}{2(x-1)(x+1)}=
=\frac{12x^2-13x-11}{2(x^2-1)}
f)
\frac{2x+1}{6-x} -\frac{3-2x}{x+6}=\frac{(2x+1)(x+6)-(3-2x)(6-x)}{(6-x)(x+6)}=
=\frac{2x^2+12x+x+6-(18-3x-12x+2x^2)}{(6-x)(x+6))}=
=\frac{2x^2+13x+6-18+15x-2x^2}{-(x-6)(x+6)}=
=\frac{28x-12}{-(x^2-36)}=-\frac{4(7x-3)}{x^2-36}