a)
\frac{6a-5}{3}+3-5a=2a-5+3-3a=-3a-2
b)
\frac{12b-9}{3}+\frac{12b-8}{2}=4b-3+6b-4=10b-7
c)
5n^2-2n-\frac{4n^2+40n}{8}=5n^2-2n-(0,5n^2+5n)=5n^2-2n-0,5n^2-5n=4,5n^2-7n
d)
\frac{8m^2-10}{2}-\frac{20m^2+15}{5}=4m^2-5-(4m^2+3)=4m^2-5-4m^2-3=-8
e)
3x^2+4+\frac{1}{7}*\frac{14x^2-21}{6}=3x^2+4+\frac{1}{7}*\frac{7(2x^2-3)}{6}=
3x^2+4+\frac{1}{3}x^2-\frac{1}{2}=3\frac{1}{3}x^2+3\frac{1}{2}
f)
\frac{15p^2-9p}{6}-6*\frac{1-6p}{4}=\frac{15}{6}p^2-\frac{9p}{6}-\frac{3(1-6p)}{2}=
2\frac{3}{6}p^2-1\frac{3}{6}p-\frac{3-18p}{2}=2,5p^2-1,5p-1,5+9p=2,5p^2+7,5p-1,5