28.
\(\frac{2^7.9^3}{6^5.8^3}=\frac{2^7.(3^2)^3}{2^5.3^5.(2^3)^3}=\frac{2^7.3^6}{2^{14}.3^5}=\frac{3}{2^7}\)
29.
\(\frac{6^{15}.3^{10}}{4^7.9^{13}}=\frac{2^{15}.3^{15}.3^{10}}{(2^2)^7.(3^2)^{13}}=\frac{2^{15}.3^{25}}{2^{14}.3^{26}}=\frac{2}{3}\)
30.
\(\frac{2^{12}.27^{15}}{32^2.3^{45}}=\frac{2^{12}.(3^3)^{15}}{(2^5)^2.3^{45}}=\frac{2^{12}.3^{45}}{2^{10}.3^{45}}=2^2=4\)