$\frac{15a(p-q)}{20b(p-q)}=\frac{15}{20}\ast a\ast \frac{1}{b}\ast \frac{p-q}{p-q}=\frac{3a}{4b}$

$\frac{8a^2{b}^3(a+b)}{20a{b}^2(a+b)}=\frac{8}{20}\ast \frac{a^2}{a}\ast \frac{b^3}{b^2}\ast \frac{a+b}{a+b}=\frac{2ab}{5}$

$\frac{2b(m+n)}{6bc(m+n)}=\frac{2}{6}\ast \frac{b}{b}\ast \frac{1}{c}\ast \frac{m+n}{m+n}=\frac{1}{3c}$

$\frac{44c^3{d}^8(c-d)}{100c^5{d}^4(c-d)}=\frac{44}{100}\ast \frac{c^3}{c^5}\ast \frac{d^8}{d^4}\ast \frac{c-d}{c-d}=\frac{11d^4}{25c^2}$